scons/windows: Enable compute shaders when possible.

Closed Prodea Alexandru-Liviu requested to merge pal1000/mesa:windows-compute-shaders into master

Tests done with llvm-config indicate that there are only 2 libraries in irreader and not in engine, LLVMAsmParser and LLVMIRReader and both of them are part of coroutines so I replaced irreader with coroutines and added libraries unique to coroutines.

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