universal binary instructions

[chriseppstein]

On Lion I had to do the following in order to get a universal binary built and installed. Also I got a wierd error during rubygems installation at the tail end of the install, but so far it hasn't affected me.

brew install autoconf
export PATH=/usr/local/Cellar/autoconf/2.68/bin:$PATH
export CC=/usr/bin/gcc-4.2
rvm install ruby-1.9.2-head-n_ub -C --with-arch=x86_64,i386

[chriseppstein]

Note: I put this here because I didn't see a way to edit the wiki.