Mac Rmagick won't install with Xcode 4.2
Solution 1:
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.
Solution 2:
I tried to download and install 4.1 for lion and this didn't even install (without a proper error message). Now a colleague gave me this great link to GCC for Mac which worked like a charm: https://github.com/kennethreitz/osx-gcc-installer
Don't forget to download the v2 if you run on > 10.7.0
Solution 3:
For people who want source installation, you can download the source code repository and issue this command in the imagemagick source code directory.
./configure --disable-openmp
It will work similar to the brew version above but with source code compilation instead.