[compiler-rt] [asan] Rewrite Windows/heaprealloc_alloc_zero check to avoid dereference (PR #156211)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> LGTM, thanks! This does seem to fix the test for me.
> 
> (Side note - is the `UNSUPPORTED: asan-64-bits` still relevant here you think?)

I checked; before b3452d90b043a398639e62b0ab01aa339cc649de, this test did indeed fail on 64 bit. With the recent changes and this fix, this test does pass on 64 bit as well, so the `UNSUPPORTED` marking can be removed at the same time.

https://github.com/llvm/llvm-project/pull/156211