[swift-dev] Way to --clean only the Swift parts of Swift?

[Alexis]

I find that build-script tends to get corrupted state very easily, forcing me to do a —clean build. This is usually because of git, but seemingly from benign things like checking out HEAD~1. Since I’m working on the stdlib, the corruption often shows up in there, so —clean is needlessly heavy-handed. I don’t need to rebuild clang or llvm, and I probably don’t need to rebuild swiftc. Is there any way to do this?