Don't fail-fast on master builds for the general matrix.

[akrieger]

Summary

None

Purpose of change

The mac osx build is more pedantic than the others and can fail at compile time when the others don't. If this happens on a master branch build though, it'll cancel the rest of the matrix jobs, which will then not upload artifacts to cache and will slowdown all future builds until a green master happens again. That sucks.

Describe the solution

Set fail-fast to false when on a master build so all build jobs attempt to make progress. This is fine because we now have better usage of github's concurrent actions functionality to prevent extraneous master branch work, so we can afford to have all the jobs eventually failing in case of a global build failure.

Describe alternatives you've considered

Nada.

Testing

Pushed to my master branch on the current broken build and the outstanding builds did not get cancelled when the osx build failed. https://github.com/akrieger/Cataclysm-DDA/actions/runs/1796382056

Additional context