[compiler-rt] [ASan] return 0 for current allocated bytes if malloc/free are never happend (PR #67394)

[Mitch Phillips via llvm-commits]

hctim wrote:

This looks reasonable, and I don't think we're going to be able to understand the original justification behind `1` (the change was made in [2013](https://github.com/llvm/llvm-project/commit/920b3b9a0cf15) by Alexey, who's no longer around).

Can you also patch up `__sanitizer_get_free_bytes` while you're here? Other than that, LGTM.

https://github.com/llvm/llvm-project/pull/67394