[compiler-rt] [asan] Detect dereferencing zero-alloc as heap buffer overflow (PR #155943)

[Hans Wennborg via llvm-commits]

zmodem wrote:

It broke Mac too: https://green.lab.llvm.org/job/llvm.org/job/clang-stage1-RA/5301/testReport/junit/AddressSanitizer-x86_64-darwin/TestCases/zero_alloc_cpp/

Could it just include `<stdlib.h>` instead of `<malloc.h>`?

I'll mark it unsupported on mac for now.

https://github.com/llvm/llvm-project/pull/155943