[Support] PR42623: Avoid setting the delete-on-close bit if a TempFil…

…e doesn't reside on a local drive

On Windows, after commit 881ba10, tools
using TempFile would error with "bad file descriptor" when writing the
file on a network drive. It appears that setting the delete-on-close bit via
SetFileInformationByHandle/FileDispositionInfo prevented it from
accessing the file on network drives, and although using
FILE_DISPOSITION_INFO seems to work, it causes other troubles.

Differential Revision: https://reviews.llvm.org/D81803

llvm/lib/Support/Windows/Path.inc

@@ -402,6 +402,20 @@ std::error_code is_local(int FD, bool &Result) {
 }
 
 static std::error_code setDeleteDisposition(HANDLE Handle, bool Delete) {
+  // First, check if the file is on a network (non-local) drive. If so, don't
+  // set DeleteFile to true, since it prevents opening the file for writes.
+  SmallVector<wchar_t, 128> FinalPath;
+  if (std::error_code EC = realPathFromHandle(Handle, FinalPath))
+    return EC;
+
+  bool IsLocal;
+  if (std::error_code EC = is_local_internal(FinalPath, IsLocal))
+    return EC;
+
+  if (!IsLocal)
+    return std::error_code();
+
+  // The file is on a local drive, set the DeleteFile to true.
   FILE_DISPOSITION_INFO Disposition;
   Disposition.DeleteFile = Delete;
   if (!SetFileInformationByHandle(Handle, FileDispositionInfo, &Disposition,