$ svn co https://llvm.org/svn/llvm-project/llvm/branches/release_29@127367 llvm-2.9
$ cd llvm-2.9
$ env UNIVERSAL=1 UNIVERSAL_ARCH="i386 x86_64" CC=/usr/bin/gcc CXX=/usr/bin/g++ ./configure --enable-bindings=none --enable-optimized --with-llvmgccdir=/tmp
$ env UNIVERSAL=1 UNIVERSAL_ARCH="i386 x86_64" CC=/usr/bin/gcc CXX=/usr/bin/g++ make
$ sudo env UNIVERSAL=1 UNIVERSAL_ARCH="i386 x86_64" CC=/usr/bin/gcc CXX=/usr/bin/g++ make install
$ git clone git://github.com/MacRuby/MacRuby.git
$ cd MacRuby
$ rake RC_ARCHS="i386 x86_64" jobs=2
$ sudo rake install
$ file /usr/local/bin/macruby
/usr/local/bin/macruby: Mach-O universal binary with 2 architectures
/usr/local/bin/macruby (for architecture i386): Mach-O executable i386
/usr/local/bin/macruby (for architecture x86_64): Mach-O 64-bit executable x86_64
$ arch -i386 macruby -v
MacRuby 0.11 (ruby 1.9.2) [universal-darwin10.0, i386]