Even if you don't run tests, at a bare minimum you always need to build-test. master should always build. With a warm ccache, that shouldn't take excessively long, but long enough that you still want to do it server-side.
Assuming you've locally build-tested each commit, the bot only needs to build-test the combination. And some bots even pull in a set of merges at a time, and keep them if they all pass, only falling back to serial testing if they fail.
Assuming you've locally build-tested each commit, the bot only needs to build-test the combination. And some bots even pull in a set of merges at a time, and keep them if they all pass, only falling back to serial testing if they fail.