project/qemu: Don't pass None to os.join()

If qemu.py is called without a config parameter but with a linux,
android, atf, or rpmbd parameter, the second argument to os.join
may be null which is an error. This change ensures that os.join
is only called with arguments that are not None.

Bug: None
Change-Id: I4e04cbe5dfa112d92b980d09ce82c58c5630359d
1 file changed
tree: f2c5a2ceb39f4ab9ea5f5cbad9a45cc8dcab5520
  1. project/
  2. .clang-format
  3. LICENSE
  4. PREUPLOAD.cfg