[compiler-rt] [ASan] Recognize WASI platform in sanitizer_platform.h (PR #139017)

[Yuta Saito via llvm-commits]

kateinoigakukun wrote:

Yeah, I think we can share a few things about shadow memory mapping. If you're happy, I can upstream a part of the Emscripten stuff at the same time.

https://github.com/llvm/llvm-project/pull/139017