Merge branch 'ef/mingw-rmdir'

MinGW has a workaround when rmdir unnecessarily fails to retry with
a prompt, but the logic was kicking in when the rmdir failed with
ENOTEMPTY, i.e. was expected to fail and there is no point retrying.

* ef/mingw-rmdir:
  mingw_rmdir: do not prompt for retry when non-empty

diff --cc compat/mingw.c
Simple merge