Add ninja as a default build system for some runners.

[fruffy]

Fixes #4471.

Needs a bit more work. There are lot of different build systems and options scattered around.

[vlstill]

Great to have Ninja officially supported/tested! Just two suggestions to make the CI a bit more robust.

[vlstill]

Is there a build that uses make now? I don't see any and I think it is a good idea to have one. Ubuntu unity could be a good candidate as it should be relatively fast anyway as a unity build. The non-unity could be an alternative if the speed is of concern as it does not run tests (it is hard, but not impossible, to imagine a different build system to cause bugs in the build).

[fruffy]

Is there a build that uses make now? I don't see any and I think it is a good idea to have one. Ubuntu unity could be a good candidate as it should be relatively fast anyway as a unity build. The non-unity could be an alternative if the speed is of concern as it does not run tests (it is hard, but not impossible, to imagine a different build system to cause bugs in the build).

I figured we could use the nightly sanitizer build for this: https://github.com/p4lang/p4c/blob/main/.github/workflows/ci-ubuntu-20-sanitizer-nightly.yml

I can also change the unity build to use make again.

[vlstill]

OK, I think having make just in nightly would be sufficient, I am OK with either of these choices.