rvm install 1.9.3-p194 --with-gcc=clang


Fixes this error In Mac:

```
In file included from ./include/ruby/ruby.h:64,
                 from ./include/ruby.h:32,
                 from main.c:13:
/usr/include/stdarg.h:4:25: error: stdarg.h: No such file or directory
In file included from ./include/ruby/intern.h:32,
                 from ./include/ruby/ruby.h:1382,
                 from ./include/ruby.h:32,
                 from main.c:13:
/usr/include/varargs.h:4:26: error: varargs.h: No such file or directory
make: *** [main.o] Error 1
```