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

[via llvm-commits]

enh-google wrote:

i worry a bit about the proximity of "allow removing" and "make it easy for the actual Android llvm build to fuck up and accidentally ship with all the __isOSVersionAtLeast() stuff broken".

i guess i don't really understand the upside to this, and the downside for the actual shipping configuration worries me.

if this is useful, should it be a separate _opt-in_ option?

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