I just got a new macbook pro and trying to setup my dev environment. I downloaded xcode 4.2 from the app store and installed it, after this i installed homebrew and RVM. Ima
I tried your solution (full of hope) but It did not work for me unfortunately. Finally I managed to make it work by reinstalling imagemagick without openmp support (this is the library responsible for lgomp)
using Homebrew:
brew install imagemagick --disable-openmp
then rmagick installed without any problems.