#include <stdio.h>
#include <windows.h>

int main() {
  if (!DeleteFileA("testDir")) {
    printf("GetLastError %d\n", GetLastError());
  }

  if (_unlink("testDir") != 0) {
    printf(_strerror(NULL));
    printf("Errno: %d\n", errno);
  }
}

C:\Users\jmittertreiner\tmp\testRm> mkdir testDir
C:\Users\jmittertreiner\tmp\testRm>cl .\testrm.cpp  && .\testrm.exe
Microsoft (R) C/C++ Optimizing Compiler Version 19.16.27024.1 for x86
Copyright (C) Microsoft Corporation.  All rights reserved.

testrm.cpp
Microsoft (R) Incremental Linker Version 14.16.27024.1
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:testrm.exe
testrm.obj
GetLastError 5
Permission denied
Errno: 13