Error messages when I do "brew upgrade" in OS X Mavericks.

brew upgrade -v

$ brew upgrade -v
==> Upgrading 2 outdated packages, with result:
serf 1.2.1, subversion 1.7.10
==> Upgrading serf
==> Downloading http://serf.googlecode.com/files/serf-1.2.1.tar.bz2
Already downloaded: /Library/Caches/Homebrew/serf-1.2.1.tar.bz2
tar xf /Library/Caches/Homebrew/serf-1.2.1.tar.bz2
==> ./configure --prefix=/usr/local/Cellar/serf/1.2.1 --with-apr=/usr/local/Library/ENV/4.3
./configure --prefix=/usr/local/Cellar/serf/1.2.1 --with-apr=/usr/local/Library/ENV/4.3
checking for chosen layout... Serf
checking for working mkdir -p... yes
checking build system type... x86_64-apple-darwin13.0.0
checking host system type... x86_64-apple-darwin13.0.0
checking target system type... x86_64-apple-darwin13.0.0

Configuring Apache Portable Runtime library...

checking for APR... yes
  setting CPP to "/Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc -E"
  setting APR_LIBTOOL to "/usr/share/apr-1/build-1/libtool"
  setting CFLAGS to " "
  setting CPPFLAGS to " -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK"
  setting LDFLAGS to " "
  setting LTFLAGS to "--silent"

Configuring Apache Portable Runtime Utility library...

checking for APR-util... yes
checking for gcc... cc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether cc accepts -g... yes
checking for cc option to accept ISO C89... none needed
checking how to run the C preprocessor... /Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc -E
configure: error: in `/private/tmp/serf-KeHQ/serf-1.2.1':
configure: error: C preprocessor "/Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc -E" fails sanity check
See `config.log' for more details
==> Configuration
HOMEBREW_VERSION: 0.9.4
HEAD: 231a297d9b5738948da59efd821fbd07ae3cb96c
CPU: 8-core 64-bit ivybridge
OS X: 10.9-x86_64
Xcode: 5.0 => /Applications/Xcode5-DP.app/Contents/Developer/
Error: Homebrew doesn't know what compiler versions ship with your version
of Xcode (5.0). Please `brew update` and if that doesn't help, file
an issue with the output of `brew --config`:
  https://github.com/mxcl/homebrew/issues

Thanks!
LLVM-GCC: build 0
Clang: 5.0 build 500
X11: 2.7.4 => /opt/X11
==> ENV
HOMEBREW_CC: clang
MAKEFLAGS: -j8
CMAKE_PREFIX_PATH: /usr/local/opt/readline:/usr/local/opt/sqlite:/usr/local
CMAKE_LIBRARY_PATH: /System/Library/Frameworks/OpenGL.framework/Versions/Current/Libraries
PKG_CONFIG_PATH: /usr/local/opt/sqlite/lib/pkgconfig
PKG_CONFIG_LIBDIR: /usr/lib/pkgconfig
ACLOCAL_PATH: /usr/local/share/aclocal
OBJC: cc
PATH: /usr/local/Library/ENV/4.3:/usr/local/opt/libtool/bin:/usr/local/opt/sqlite/bin:/usr/bin:/bin:/usr/sbin:/sbin

Error: serf did not build
Logs:       /Users/huahang/Library/Logs/Homebrew/serf/config.log

config.log

This file contains any messages produced by compilers while
running configure, to aid debugging if configure makes a mistake.

It was created by configure, which was
generated by GNU Autoconf 2.69.  Invocation command line was

  $ ./configure --prefix=/usr/local/Cellar/serf/1.2.1 --with-apr=/usr/local/Library/ENV/4.3

## --------- ##
## Platform. ##
## --------- ##

hostname = localhost
uname -m = x86_64
uname -r = 13.0.0
uname -s = Darwin
uname -v = Darwin Kernel Version 13.0.0: Sat Jun  1 01:13:40 PDT 2013; root:xnu-2422.1.4.1.8~1/RELEASE_X86_64

/usr/bin/uname -p = i386
/bin/uname -X     = unknown

/bin/arch              = unknown
/usr/bin/arch -k       = unknown
/usr/convex/getsysinfo = unknown
/usr/bin/hostinfo      = Mach kernel version:
   Darwin Kernel Version 13.0.0: Sat Jun  1 01:13:40 PDT 2013; root:xnu-2422.1.4.1.8~1/RELEASE_X86_64
Kernel configured for up to 8 processors.
4 processors are physically available.
8 processors are logically available.
Processor type: i486 (Intel 80486)
Processors active: 0 1 2 3 4 5 6 7
Primary memory available: 8.00 gigabytes
Default processor set: 185 tasks, 803 threads, 8 processors
Load average: 1.99, Mach factor: 6.00
/bin/machine           = unknown
/usr/bin/oslevel       = unknown
/bin/universe          = unknown

PATH: /usr/local/Library/ENV/4.3
PATH: /usr/local/opt/libtool/bin
PATH: /usr/local/opt/sqlite/bin
PATH: /usr/bin
PATH: /bin
PATH: /usr/sbin
PATH: /sbin


## ----------- ##
## Core tests. ##
## ----------- ##

configure:2261: checking for chosen layout
configure:2263: result: Serf
configure:2474: checking for working mkdir -p
configure:2490: result: yes
configure:2506: checking build system type
configure:2520: result: x86_64-apple-darwin13.0.0
configure:2540: checking host system type
configure:2553: result: x86_64-apple-darwin13.0.0
configure:2573: checking target system type
configure:2586: result: x86_64-apple-darwin13.0.0
configure:2643: checking for APR
configure:2722: result: yes
configure:3039: checking for APR-util
configure:3118: result: yes
configure:3377: checking for gcc
configure:3404: result: cc
configure:3633: checking for C compiler version
configure:3642: cc --version >&5
Apple LLVM version 5.0 (clang-500.1.58) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.0.0
Thread model: posix
configure:3653: $? = 0
configure:3642: cc -v >&5
Apple LLVM version 5.0 (clang-500.1.58) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.0.0
Thread model: posix
clang: warning: argument unused during compilation: '-isystem /usr/local/include'
clang: warning: argument unused during compilation: '-I /usr/local/opt/readline/include'
clang: warning: argument unused during compilation: '-I /usr/local/opt/sqlite/include'
clang: warning: argument unused during compilation: '-L/usr/local/opt/readline/lib'
clang: warning: argument unused during compilation: '-L/usr/local/opt/sqlite/lib'
clang: warning: argument unused during compilation: '-L/usr/local/lib'
clang: warning: argument unused during compilation: '-L/System/Library/Frameworks/OpenGL.framework/Versions/Current/Libraries'
... rest of stderr output deleted ...
configure:3653: $? = 0
configure:3642: cc -V >&5
clang: error: unsupported option '-V -isystem/usr/local/include'
clang: error: no input files
configure:3653: $? = 1
configure:3642: cc -qversion >&5
clang: error: no input files
configure:3653: $? = 1
configure:3673: checking whether the C compiler works
configure:3695: cc    -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK   conftest.c  >&5
configure:3699: $? = 0
configure:3747: result: yes
configure:3750: checking for C compiler default output file name
configure:3752: result: a.out
configure:3758: checking for suffix of executables
configure:3765: cc -o conftest    -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK   conftest.c  >&5
configure:3769: $? = 0
configure:3791: result: 
configure:3813: checking whether we are cross compiling
configure:3821: cc -o conftest    -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK   conftest.c  >&5
configure:3825: $? = 0
configure:3832: ./conftest
configure:3836: $? = 0
configure:3851: result: no
configure:3856: checking for suffix of object files
configure:3878: cc -c    -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK conftest.c >&5
configure:3882: $? = 0
configure:3903: result: o
configure:3907: checking whether we are using the GNU C compiler
configure:3926: cc -c    -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK conftest.c >&5
configure:3926: $? = 0
configure:3935: result: yes
configure:3944: checking whether cc accepts -g
configure:3964: cc -c -g  -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK conftest.c >&5
configure:3964: $? = 0
configure:4005: result: yes
configure:4022: checking for cc option to accept ISO C89
configure:4085: cc  -c    -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK conftest.c >&5
configure:4085: $? = 0
configure:4098: result: none needed
configure:4123: checking how to run the C preprocessor
configure:4193: result: /Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc -E
configure:4213: /Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc -E  -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK conftest.c
./configure: line 1494: /Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc: No such file or directory
configure:4213: $? = 127
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME ""
| #define PACKAGE_TARNAME ""
| #define PACKAGE_VERSION ""
| #define PACKAGE_STRING ""
| #define PACKAGE_BUGREPORT ""
| #define PACKAGE_URL ""
| /* end confdefs.h.  */
| #ifdef __STDC__
| # include <limits.h>
| #else
| # include <assert.h>
| #endif
| 		     Syntax error
configure:4213: /Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc -E  -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK conftest.c
./configure: line 1494: /Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc: No such file or directory
configure:4213: $? = 127
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME ""
| #define PACKAGE_TARNAME ""
| #define PACKAGE_VERSION ""
| #define PACKAGE_STRING ""
| #define PACKAGE_BUGREPORT ""
| #define PACKAGE_URL ""
| /* end confdefs.h.  */
| #ifdef __STDC__
| # include <limits.h>
| #else
| # include <assert.h>
| #endif
| 		     Syntax error
configure:4243: error: in `/private/tmp/serf-KeHQ/serf-1.2.1':
configure:4245: error: C preprocessor "/Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc -E" fails sanity check
See `config.log' for more details

## ---------------- ##
## Cache variables. ##
## ---------------- ##

ac_cv_build=x86_64-apple-darwin13.0.0
ac_cv_c_compiler_gnu=yes
ac_cv_env_CC_set=set
ac_cv_env_CC_value=cc
ac_cv_env_CFLAGS_set=
ac_cv_env_CFLAGS_value=
ac_cv_env_CPPFLAGS_set=
ac_cv_env_CPPFLAGS_value=
ac_cv_env_CPP_set=
ac_cv_env_CPP_value=
ac_cv_env_LDFLAGS_set=
ac_cv_env_LDFLAGS_value=
ac_cv_env_LIBS_set=
ac_cv_env_LIBS_value=
ac_cv_env_build_alias_set=
ac_cv_env_build_alias_value=
ac_cv_env_host_alias_set=
ac_cv_env_host_alias_value=
ac_cv_env_target_alias_set=
ac_cv_env_target_alias_value=
ac_cv_host=x86_64-apple-darwin13.0.0
ac_cv_mkdir_p=yes
ac_cv_objext=o
ac_cv_prog_CPP='/Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc -E'
ac_cv_prog_ac_ct_CC=cc
ac_cv_prog_cc_c89=
ac_cv_prog_cc_g=yes
ac_cv_target=x86_64-apple-darwin13.0.0

## ----------------- ##
## Output variables. ##
## ----------------- ##

APR_BINDIR='/usr/bin'
APR_CONFIG='/usr/local/Library/ENV/4.3/apr-1-config'
APR_INCLUDES=' -I/usr/include/apr-1 '
APR_LIBTOOL='/usr/share/apr-1/build-1/libtool'
APR_VERSION='1.4.5'
APU_BINDIR='/usr/bin'
APU_CONFIG='/usr/bin/apu-1-config'
APU_INCLUDES=' -I/usr/include/apr-1 '
APU_VERSION='1.3.12'
CC='cc'
CFLAGS=' '
CPP='/Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.9.xctoolchain/usr/bin/cc -E'
CPPFLAGS=' -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK'
DEFS=''
ECHO_C='\c'
ECHO_N=''
ECHO_T=''
EGREP=''
EXEEXT=''
EXTRA_CFLAGS=''
EXTRA_CPPFLAGS=''
EXTRA_CXXFLAGS=''
EXTRA_INCLUDES=''
EXTRA_LDFLAGS=''
EXTRA_LIBS=''
GREP=''
INSTALL_DATA=''
INSTALL_PROGRAM=''
INSTALL_SCRIPT=''
LDFLAGS=' '
LIBOBJS=''
LIBS=''
LTFLAGS='--silent'
LTLIBOBJS=''
OBJEXT='o'
PACKAGE_BUGREPORT=''
PACKAGE_NAME=''
PACKAGE_STRING=''
PACKAGE_TARNAME=''
PACKAGE_URL=''
PACKAGE_VERSION=''
PATH_SEPARATOR=':'
SERF_BUILD_SRCLIB_DIRS=''
SERF_CLEAN_SRCLIB_DIRS=''
SERF_DOTTED_VERSION=''
SERF_LIBS=''
SERF_MAJOR_VERSION=''
SHELL='/bin/sh'
ac_ct_CC='cc'
bindir='${exec_prefix}/bin'
build='x86_64-apple-darwin13.0.0'
build_alias=''
build_cpu='x86_64'
build_os='darwin13.0.0'
build_vendor='apple'
datadir='${prefix}'
datarootdir='${prefix}/share'
docdir='${datarootdir}/doc/${PACKAGE}'
dvidir='${docdir}'
exec_prefix='${prefix}'
host='x86_64-apple-darwin13.0.0'
host_alias=''
host_cpu='x86_64'
host_os='darwin13.0.0'
host_vendor='apple'
htmldir='${docdir}'
includedir='${prefix}/include/serf-${SERF_MAJOR_VERSION}'
infodir='${datarootdir}/info'
libdir='${exec_prefix}/lib'
libexecdir='${exec_prefix}/modules'
localedir='${datarootdir}/locale'
localstatedir='${prefix}'
mandir='${prefix}/man'
mkdir_p='mkdir -p'
oldincludedir='/usr/include'
pdfdir='${docdir}'
prefix='/usr/local/Cellar/serf/1.2.1'
program_transform_name='s,x,x,'
psdir='${docdir}'
sbindir='${exec_prefix}/bin'
sharedstatedir='${prefix}/com'
sysconfdir='${prefix}/conf'
target='x86_64-apple-darwin13.0.0'
target_alias=''
target_cpu='x86_64'
target_os='darwin13.0.0'
target_vendor='apple'

## ----------- ##
## confdefs.h. ##
## ----------- ##

/* confdefs.h */
#define PACKAGE_NAME ""
#define PACKAGE_TARNAME ""
#define PACKAGE_VERSION ""
#define PACKAGE_STRING ""
#define PACKAGE_BUGREPORT ""
#define PACKAGE_URL ""

configure: exit 1