[llvm] [LLVM] Remove explicit dependency on builtins build (PR #159854)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

> I don't know the compiler-rt/builtins system well enough to know whether theses dependencies can jsut be removed. Would't it be more elegant to avoid `BUILD_ALWAYS` in the first place?

I tried that, but as far as I can tell the `BUILD_ALWAYS` is required to keep the runtimes correctly up-to-date. CMake doesn't know anything about the internal targets. We could theoretically export stamps manually, but since there's tons of targets that vary by what the user requested it'd be quite difficult to rig together.

In practice if you remove BUILD_ALWAYS and modify the runtimes source, you will need to manually retrigger a build from the runtimes directory, the root one will just say 'no work to do'.

https://github.com/llvm/llvm-project/pull/159854