Well I didn’t try Mountain Lion, but I did make a new effort to compile Carrara plug-ins under XCode 4 so I feel more comfortable about the risk of no access to XCode 3. This link got me mostly there
but there were a couple other things I needed to do.
1. Looks like GCC 4.2 got removed in between when that was written and 4.4. I had to do similar steps to the Restoring GCC 4.0 to restore GCC 4.2. You’ll need to create the symlinks one at a time since there are other 4.2 named things in the XCode 3 folder. XCode 4’s GCC 4.2 plug-in has to be replaced too.
2. I had to replace the XCode 4 as and ld in /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin with the XCode 3 versions to get PPC targets to build. I just backed them up and created symlinks. There’s probably not a lot of folks out there still using PPC, and I don’t even have a place to test them any more. However I have at least one vocal evangelistic customer still on PPC so I still try to keep that target in my build even though I won’t officially support it. It may not be an issue for others.
I was able to build everything C6-C8 and XCode 4 didn’t crash like XCode 3 regularly does for me under Lion.