[compiler-rt] Silence warnings when building with Clang ToT

Fixes several warnings such as:
```
C:\git\llvm-project\compiler-rt\lib\profile\InstrProfilingFile.c(760,18): warning: cast from 'const char *' to 'void *' drops const qualifier [-Wcast-qual]
  760 |     free((void *)lprofCurFilename.FilenamePat);
      |                  ^
3 warnings generated.
```