[lit] [windows] Make sure to convert all path separators to backslashes in NT style \\?\... paths

[mstorsjo]

Summary

E.g. the mingw python distributed in msys2 (the mingw one, which is a normal win32 application and doesn't use the msys2 runtime itself), despite being a normal win32 python, still uses forward slashes. This works fine for other cases, but when constructing a raw NT path, all path separators must be backslashes.

[mstorsjo]

Admittedly, this python doesn't really pass all tests anyway, as some tests rely on path formatting to match between different components - but it does help running some number of tests with it at least.

[rnk]

lgtm

llvm/utils/lit/lit/util.py

157

I feel like path.replace('/', '\\') would be the more obvious spelling (fewer temporary strings), but they are functionally equivalent.

[mstorsjo]

llvm/utils/lit/lit/util.py

157

Ah, yes, will change it to that form before pushing the change. Thanks!

llvm/utils/lit/lit/util.py

 
 def mkdir(path):
     try:
         if platform.system() == 'Windows':
             from ctypes import windll
             from ctypes import GetLastError, WinError
 
             path = os.path.abspath(path)
+            # Make sure that the path uses backslashes here, in case
+            # python would have happened to use forward slashes, as the
+            # NT path format only supports backslashes.
+            path = path.replace('/', '\\')
             NTPath = to_unicode(r'\\?\%s' % path)
             if not windll.kernel32.CreateDirectoryW(NTPath, None):
                 raise WinError(GetLastError())
         else:
             os.mkdir(path)
     except OSError:
         e = sys.exc_info()[1]
         # ignore EEXIST, which may occur during a race condition