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?