[compiler-rt] Reland "[rtsan] Intercept aligned_alloc on all versions of OSX if available on the build machine" (PR #114153)

[Chris Apple via llvm-commits]

================
@@ -464,10 +464,13 @@ INTERCEPTOR(void *, valloc, SIZE_T size) {
 }
 
 #if SANITIZER_INTERCEPT_ALIGNED_ALLOC
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunguarded-availability-new"
----------------
cjappl wrote:

(sorry, I totally misread what you were saying)

Yes, aligned_alloc is weakly linked. I'll add this to the comment

```
> nm -m lib/clang/20/lib/darwin/libclang_rt.rtsan_osx_dynamic.dylib | grep aligned | grep weak
                 (undefined) weak external _aligned_alloc (from libSystem)
```

https://github.com/llvm/llvm-project/pull/114153