Unaddressable error beyond TOS reported for variable-length automatic arrays in MinGW

Hello,

Thanks a lot for your work on Drmemory!

I'm using msys2+mingw64, and Drmemory reports an error on every variable-length automatic array.

Example:
```
size_t count = 0;
/* ... compute count ... */
int myarray[count]; // Drmemory reports "UNADDRESSABLE ACCESS beyond top of stack"
```