PCH: Generate sources during Compute step

Source/cmFileAPICodemodel.cxx

Source/cmGeneratorTarget.cxx

Source/cmGeneratorTarget.h

Source/cmGlobalGenerator.cxx

Source/cmGlobalXCodeGenerator.cxx

Source/cmLocalGenerator.cxx

Source/cmLocalGenerator.h

Source/cmLocalVisualStudio7Generator.cxx

Source/cmMakefileExecutableTargetGenerator.cxx

Source/cmMakefileLibraryTargetGenerator.cxx

Source/cmMakefileTargetGenerator.cxx

Source/cmMakefileUtilityTargetGenerator.cxx

Source/cmNinjaNormalTargetGenerator.cxx

Source/cmNinjaTargetGenerator.cxx

Source/cmVisualStudio10TargetGenerator.cxx