rbenv_install_1_9_2_on_yosemite

rubyinstall.sh

rbenv install 1.9.2-p330
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer//usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Downloading ruby-1.9.2-p330.tar.gz...
-> http://dqw8nmjcqpjn7.cloudfront.net/23ef45fdaecc5d6c7b4e9e2d51b23817fc6aa8225a20f123f7fa98760e8b5ca9
Installing ruby-1.9.2-p330...

BUILD FAILED (OS X 10.10 using ruby-build 20140919)

Inspect or clean up the working tree at /var/folders/ns/3sn8y8fn1k5crc9l0f1_dqvr0000gp/T/ruby-build.20141021173322.89970
Results logged to /var/folders/ns/3sn8y8fn1k5crc9l0f1_dqvr0000gp/T/ruby-build.20141021173322.89970.log

Last 10 log lines:
/var/folders/ns/3sn8y8fn1k5crc9l0f1_dqvr0000gp/T/ruby-build.20141021173322.89970/ruby-1.9.2-p330 /var/folders/ns/3sn8y8fn1k5crc9l0f1_dqvr0000gp/T/ruby-build.20141021173322.89970 ~/Sites/
configure: WARNING: unrecognized options: --with-libyaml-dir, --with-readline-dir
checking build system type... i386-apple-darwin14.0.0
checking host system type... i386-apple-darwin14.0.0
checking target system type... i386-apple-darwin14.0.0
checking whether the C compiler works... no
configure: error: in `/var/folders/ns/3sn8y8fn1k5crc9l0f1_dqvr0000gp/T/ruby-build.20141021173322.89970/ruby-1.9.2-p330':
configure: error: C compiler cannot create executables
See `config.log' for more details
make: *** No targets specified and no makefile found.  Stop.

Same error here with RVM :(

In my personal computer I get a different error message:

rbenv install 1.9.2-p330
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include/c++/4.2.1

ERROR: This package must be compiled with GCC, but ruby-build couldn't
find a suitable `gcc` executable on your system. Please install GCC
and try again.

DETAILS: Apple no longer includes the official GCC compiler with Xcode
as of version 4.2. Instead, the `gcc` executable is a symlink to
`llvm-gcc`, a modified version of GCC which outputs LLVM bytecode.

For most programs the `llvm-gcc` compiler works fine. However,
versions of Ruby older than 1.9.3-p125 are incompatible with
`llvm-gcc`. To build older versions of Ruby you must have the official
GCC compiler installed on your system.

TO FIX THE PROBLEM: Install Homebrew's apple-gcc42 package with this
command: brew tap homebrew/dupes ; brew install apple-gcc42

You will need to install the official GCC compiler to build older
versions of Ruby even if you have installed Apple's Command Line Tools
for Xcode package. The Command Line Tools for Xcode package only
includes `llvm-gcc`.

BUILD FAILED (OS X 10.10 using ruby-build 20140926)

Did you already tried this?

It seems that for Ruby older than 1.9.3-p547 you will need to change your compiler (gcc) to install this version.

I've tried to install a 1.9.3 and worked fine with built-in gcc:

rbenv install 1.9.3-p547
Downloading ruby-1.9.3-p547.tar.gz...
-> http://dqw8nmjcqpjn7.cloudfront.net/9ba118e4aba04c430bc4d5efb09b31a0277e101c9fd2ef3b80b9c684d7ae57a1
Installing ruby-1.9.3-p547...
Installed ruby-1.9.3-p547 to /Users/wolcanus/.rbenv/versions/1.9.3-p547

I think you can go to 1.9.3-p547 without problems, check this changelog:

• a focus has been placed on performance with file loading, File and Pathname all significantly improved
• Ruby 1.9.2 mostly fixed down the language specification for 1.9; 1.9.3 is mostly work on a 'better implementation'
• you can tune the garbage collector via environment variables (more on this in a post coming soon!)
• Ruby's license changes from dual Ruby + GPLv2 to dual Ruby + 2-clause BSD
• improved GC performance with a lazy garbage collector
• a 'better strategy' for the GIL / GVL
• test/unit supports parallel testing
• Random.rand tweaks (and rand() now accepts ranges)
• io/console, a new library in the stdlib
• 4 new encodings (so far) - cp950, cp951, UTF-16, and UTF-32
• extra String methods
• a number of tweaks to formatting strings
• Module#private_constant and Module#public_constant
• a smattering of other bits and pieces, but this is the TLDR overview!

Source: Be Prepared for Ruby 1.9.3 and 1.9.4: What’s New and What’s Different

@squiter, check this: rbenv/ruby-build#648