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

This fixes:
```
[24/47] Generating SANITIZER_TEST_OBJECTS.sanitizer_bitvector_test.cpp.i386.o
C:/git/llvm-project/compiler-rt/lib/sanitizer_common/tests/sanitizer_bitvector_test.cpp:74:29: warning: format specifies type 'size_t' (aka 'unsigned int') but the argument has type 'value_type' (aka 'unsigned long') [-Wformat]
   74 |     fprintf(stderr, "%zu ", *it);
      |                      ~~~    ^~~
      |                      %lu
1 warning generated.
```