Error while compiling Mojave experimental patch

Console Error

==> Cloning https://github.com/LouisBrunner/valgrind-macos.git
Updating /Users/Aaron/Library/Caches/Homebrew/valgrind--git
==> Checking out branch master
Already on 'master'
Your branch is up to date with 'origin/master'.
HEAD is now at 2220a31 Add README and Brew formula
==> ./autogen.sh
==> ./configure --prefix=/usr/local/Cellar/valgrind/HEAD-2220a31 --enable-only64bit --build=amd64-darwin
==> make
Last 15 lines from /Users/Aaron/Library/Logs/Homebrew/valgrind/03.make:
clang -DHAVE_CONFIG_H -I. -I..  -I.. -I../include -I../include -I../VEX/pub -I../VEX/pub -DVGA_amd64=1 -DVGO_darwin=1 -DVGP_amd64_darwin=1 -DVGPV_amd64_darwin_vanilla=1  -Ipriv   -arch x86_64 -O2 -g -Wall -Wmissing-prototypes -Wshadow -Wpointer-arith -Wstrict-prototypes -Wmissing-declarations -Wcast-align -Wcast-qual -Wwrite-strings -Wempty-body -Wformat -Wformat-security -Wignored-qualifiers -Wenum-conversion -finline-functions -fno-stack-protector -fno-strict-aliasing -fno-builtin -Wno-cast-align -Wno-self-assign -Wno-tautological-compare -mmacosx-version-min=10.6  -Wbad-function-cast -fstrict-aliasing  -c -o priv/libvex_amd64_darwin_a-host_s390_isel.o `test -f 'priv/host_s390_isel.c' || echo './'`priv/host_s390_isel.c
clang -DHAVE_CONFIG_H -I. -I..  -I.. -I../include -I../include -I../VEX/pub -I../VEX/pub -DVGA_amd64=1 -DVGO_darwin=1 -DVGP_amd64_darwin=1 -DVGPV_amd64_darwin_vanilla=1  -Ipriv   -arch x86_64 -O2 -g -Wall -Wmissing-prototypes -Wshadow -Wpointer-arith -Wstrict-prototypes -Wmissing-declarations -Wcast-align -Wcast-qual -Wwrite-strings -Wempty-body -Wformat -Wformat-security -Wignored-qualifiers -Wenum-conversion -finline-functions -fno-stack-protector -fno-strict-aliasing -fno-builtin -Wno-cast-align -Wno-self-assign -Wno-tautological-compare -mmacosx-version-min=10.6  -Wbad-function-cast -fstrict-aliasing  -c -o priv/libvex_amd64_darwin_a-s390_disasm.o `test -f 'priv/s390_disasm.c' || echo './'`priv/s390_disasm.c
clang -DHAVE_CONFIG_H -I. -I..  -I.. -I../include -I../include -I../VEX/pub -I../VEX/pub -DVGA_amd64=1 -DVGO_darwin=1 -DVGP_amd64_darwin=1 -DVGPV_amd64_darwin_vanilla=1  -Ipriv   -arch x86_64 -O2 -g -Wall -Wmissing-prototypes -Wshadow -Wpointer-arith -Wstrict-prototypes -Wmissing-declarations -Wcast-align -Wcast-qual -Wwrite-strings -Wempty-body -Wformat -Wformat-security -Wignored-qualifiers -Wenum-conversion -finline-functions -fno-stack-protector -fno-strict-aliasing -fno-builtin -Wno-cast-align -Wno-self-assign -Wno-tautological-compare -mmacosx-version-min=10.6  -Wbad-function-cast -fstrict-aliasing  -c -o priv/libvex_amd64_darwin_a-host_mips_defs.o `test -f 'priv/host_mips_defs.c' || echo './'`priv/host_mips_defs.c
clang -DHAVE_CONFIG_H -I. -I..  -I.. -I../include -I../include -I../VEX/pub -I../VEX/pub -DVGA_amd64=1 -DVGO_darwin=1 -DVGP_amd64_darwin=1 -DVGPV_amd64_darwin_vanilla=1  -Ipriv   -arch x86_64 -O2 -g -Wall -Wmissing-prototypes -Wshadow -Wpointer-arith -Wstrict-prototypes -Wmissing-declarations -Wcast-align -Wcast-qual -Wwrite-strings -Wempty-body -Wformat -Wformat-security -Wignored-qualifiers -Wenum-conversion -finline-functions -fno-stack-protector -fno-strict-aliasing -fno-builtin -Wno-cast-align -Wno-self-assign -Wno-tautological-compare -mmacosx-version-min=10.6  -Wbad-function-cast -fstrict-aliasing  -c -o priv/libvex_amd64_darwin_a-host_mips_isel.o `test -f 'priv/host_mips_isel.c' || echo './'`priv/host_mips_isel.c
clang -DHAVE_CONFIG_H -I. -I..  -I.. -I../include -I../include -I../VEX/pub -I../VEX/pub -DVGA_amd64=1 -DVGO_darwin=1 -DVGP_amd64_darwin=1 -DVGPV_amd64_darwin_vanilla=1  -Ipriv   -arch x86_64 -O2 -g -Wall -Wmissing-prototypes -Wshadow -Wpointer-arith -Wstrict-prototypes -Wmissing-declarations -Wcast-align -Wcast-qual -Wwrite-strings -Wempty-body -Wformat -Wformat-security -Wignored-qualifiers -Wenum-conversion -finline-functions -fno-stack-protector -fno-strict-aliasing -fno-builtin -Wno-cast-align -Wno-self-assign -Wno-tautological-compare -mmacosx-version-min=10.6  -Wbad-function-cast -fstrict-aliasing  -c -o priv/libvexmultiarch_amd64_darwin_a-multiarch_main_main.o `test -f 'priv/multiarch_main_main.c' || echo './'`priv/multiarch_main_main.c
rm -f libvexmultiarch-amd64-darwin.a
/usr/bin/ar cru libvexmultiarch-amd64-darwin.a priv/libvexmultiarch_amd64_darwin_a-multiarch_main_main.o 
ranlib libvexmultiarch-amd64-darwin.a
rm -f libvex-amd64-darwin.a
/usr/bin/ar cru libvex-amd64-darwin.a priv/libvex_amd64_darwin_a-main_globals.o priv/libvex_amd64_darwin_a-main_main.o priv/libvex_amd64_darwin_a-main_util.o priv/libvex_amd64_darwin_a-ir_defs.o priv/libvex_amd64_darwin_a-ir_inject.o priv/libvex_amd64_darwin_a-ir_match.o priv/libvex_amd64_darwin_a-ir_opt.o priv/libvex_amd64_darwin_a-guest_generic_bb_to_IR.o priv/libvex_amd64_darwin_a-guest_generic_x87.o priv/libvex_amd64_darwin_a-guest_x86_helpers.o priv/libvex_amd64_darwin_a-guest_x86_toIR.o priv/libvex_amd64_darwin_a-guest_amd64_helpers.o priv/libvex_amd64_darwin_a-guest_amd64_toIR.o priv/libvex_amd64_darwin_a-guest_ppc_helpers.o priv/libvex_amd64_darwin_a-guest_ppc_toIR.o priv/libvex_amd64_darwin_a-guest_arm_helpers.o priv/libvex_amd64_darwin_a-guest_arm_toIR.o priv/libvex_amd64_darwin_a-guest_arm64_helpers.o priv/libvex_amd64_darwin_a-guest_arm64_toIR.o priv/libvex_amd64_darwin_a-guest_s390_helpers.o priv/libvex_amd64_darwin_a-guest_s390_toIR.o priv/libvex_amd64_darwin_a-guest_mips_helpers.o priv/libvex_amd64_darwin_a-guest_mipsdsp_toIR.o priv/libvex_amd64_darwin_a-guest_mips_toIR.o priv/libvex_amd64_darwin_a-host_generic_regs.o priv/libvex_amd64_darwin_a-host_generic_simd64.o priv/libvex_amd64_darwin_a-host_generic_simd128.o priv/libvex_amd64_darwin_a-host_generic_simd256.o priv/libvex_amd64_darwin_a-host_generic_maddf.o priv/libvex_amd64_darwin_a-host_generic_reg_alloc2.o priv/libvex_amd64_darwin_a-host_generic_reg_alloc3.o priv/libvex_amd64_darwin_a-host_x86_defs.o priv/libvex_amd64_darwin_a-host_x86_isel.o priv/libvex_amd64_darwin_a-host_amd64_defs.o priv/libvex_amd64_darwin_a-host_amd64_isel.o priv/libvex_amd64_darwin_a-host_ppc_defs.o priv/libvex_amd64_darwin_a-host_ppc_isel.o priv/libvex_amd64_darwin_a-host_arm_defs.o priv/libvex_amd64_darwin_a-host_arm_isel.o priv/libvex_amd64_darwin_a-host_arm64_defs.o priv/libvex_amd64_darwin_a-host_arm64_isel.o priv/libvex_amd64_darwin_a-host_s390_defs.o priv/libvex_amd64_darwin_a-host_s390_isel.o priv/libvex_amd64_darwin_a-s390_disasm.o priv/libvex_amd64_darwin_a-host_mips_defs.o priv/libvex_amd64_darwin_a-host_mips_isel.o 
ranlib libvex-amd64-darwin.a
Making all in coregrind
make[2]: *** No rule to make target `/usr/include/mach/mach_vm.defs', needed by `m_mach/mach_vmUser.c'.  Stop.
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2

Do not report this issue to Homebrew/brew or Homebrew/core!

I figured it out now: I had Xcode 11 Beta 5 selected via xcode-select and that was causing the error. After selecting Xcode 10.2 all worked well. Thanks for your help @LouisBrunner!