[Sanitizer] Use CreateDirectoryA for report dirs

Using `_mkdir` of CRT in Asan Init leads to launch failure and hanging in Windows.

You can trigger it by calling:
> set ASAN_OPTIONS=log_path=a/a/a
> .\asan_program.exe

And their crash dump shows the following stack trace:
```
_guard_dispatch_icall_nop()
__acrt_get_utf8_acp_compatibility_codepage()
_mkdir(const char * path)
```

I guess there could be a cfg guard in CRT, which may lead to calling uninitialized cfg guard function address. Also, `_mkdir` supports UTF-8 encoding of the path and calls _wmkdir, but that's not necessary for this case since other file apis in sanitizer_win.cpp assumes only ANSI code case, so it makes sense to use CreateDirectoryA matching other file api calls in the same file.

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D114760