how to modify the number of parallel compilation with Xcode

Question

How to change the number of parallel compilations when building a C++ project with XCode ?

I am not talking about distributed builds, but on simultaneous compilations of

Answer 1

For command line builds, I've tested the 2011/Jul mailing list post that Mimika linked, and deployed it on our (Xcode 4.2, on Snow Leopard) build server to save memory like so:

defaults write xcodebuild IDEBuildOperationMaxNumberOfConcurrentCompileTasks 1