[compiler-rt] Fix __isOSVersionAtLeast for Android (PR #80496)

[Dan Albert via llvm-commits]

DanAlbert wrote:

Right now you use `__builtin_available(android 10000)`. That will never cause an unavailable function to be called. After this patch, you would be able to write `__builtin_available(android N+2)`, and that would cause unavailable functions in some configurations, which would crash. `__builtin_available` currently protects you from calling unavailable functions. After this change it would not do that.

Is my understanding wrong, or are you saying that's not a regression?

https://github.com/llvm/llvm-project/pull/80496