[compiler-rt] [compiler-rt] allow removing libc dependency on Android (PR #152394)

[via llvm-commits]

enh-google wrote:

> The upside is that we have an initial compiler-rt without a dependency to libc, which is useful for building Bionic libc.

as the main bionic maintainer for the last 10+ years, this is the bit i don't get --- bionic builds just fine :-)

(but this is also why i added pirama, because he owns the "building llvm" side of android, and he might be familiar with whatever llvm bootstrapping problem (?) you're talking about...)

https://github.com/llvm/llvm-project/pull/152394