unit-test.py: allow code format check only

Some OpenBMC repos use unit-test.py for the code formatting only and do
not use one of the supported build environments. Ensure this use case
still works.

Tested:
Verified all worked fine against meson based repo and also verified it
now works against openbmc-test-automation (unsupported build env)

Change-Id: Ie8af04daaee76b9ecde1e55d312d010338d1d2de
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
1 file changed