Long Compile Times of Toolchain Rebuilds

When trying to re-build a toolchain with no to a minimum set of changes it seems like that the compilation for the Swift components is triggered no matter if they are changed or not.

While small C++ changes compile in a few seconds to minutes, the compilation of the the Swift components takes about an hour on my M1 Mac. The worst part about it is that a rebuild of certain Swift components seems to be triggered no matter what. Is that a bug or some intended behaviour for Swift?


What exact command do you use to rebuild the toolchain?

I am using the swift/utils/build-toolchain script. I know that there are some faster alternatives to build certain aspects of the toolchain but I am not sure in which way, e.g., using ninja would affect the creation of universal binaries.