format-code: halt on missing linter

From a CI perspective, we want to halt if any of the tools are missing
from the docker image, as a sanity check that we did not mess that up.
Add an option (--allow-missing) that will simply warn and continue if
any linters are missing, but halt by default.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I1e39fcf80512f86679a2352a5eb29155df08162f
1 file changed