I've been trying to find a solution to this for a few days now and no luck. If anyone has been successful installing the libv8 gem for REE 1.8.7 on ML, could you please let me know the process you followed? 

I have both the XCode LLVM compiler as well as the kennethreitz GCC package for 10.7+ v2 installed.

The output when trying to install with native extensions is:

```

Building native extensions.  This could take a while...
ERROR:  Error installing libv8:
    ERROR: Failed to build gem native extension.

        /Users/XXXXX/.rvm/rubies/ree-1.8.7-2012.02/bin/ruby extconf.rb
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
    --with-opt-dir
    --without-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/Users/XXXXX/.rvm/rubies/ree-1.8.7-2012.02/bin/ruby
extconf.rb:13: uninitialized constant Gem (NameError)
Checking for Python...

Gem files will remain installed in /Users/XXXXX/.rvm/gems/ree-1.8.7-2012.02/gems/libv8-3.3.10.4 for inspection.
Results logged to /Users/XXXXX/.rvm/gems/ree-1.8.7-2012.02/gems/libv8-3.3.10.4/ext/libv8/gem_make.out
```

(The results logged are the exact same as the error).