mkqt5bld: Fix warnings reported by pylint

  W:658,0: Anomalous backslash in string: '\d'. String constant might be missing an r prefix.
  W:674,0: Anomalous backslash in string: '\.'. String constant might be missing an r prefix.

Change-Id: Ifc07f6de91b42ccc68a92247964af36d1fa59067
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>