Get 'compileas' working when using a 'filter "files: ..."' scope.

[ratzlaff]

Extends compileas to be used in file filters

  project "main"
      language "C++"

      files  { "src/file.c" }
      filter { "files:src/file.c" }
          compileas "C++"

[samsinsane]

It seems like there might be some unrelated changes in the gmake action. I'm not sure if there's much value in adding support for this to gmake given that gmake2 is intended to replace it.

Also, your new gmake2 tests aren't as comprehensive as the gmake tests, could you flesh them out the same way?

[samsinsane]

This seems to be an unrelated change? I think this is how it used to be but it was causing issues when running multiple jobs.

[tvandijck]

LGTM, I'm deferring to someone else to review/test this however.

[samsinsane]

To be honest, everything except for the gmake changes LGTM. I don't understand enough about the gmake generator to know if something will break - I'll mark this as approved, but hopefully @starkos or @TurkeyMan can chime in on the gmake changes. (For what it's worth, the gmake2 changes make sense!)

[starkos]

The gmake changes look reasonable. I do think the time has come to consider deprecating gmake for gmake2, but I'll open a separate issue for that.

[tdesveauxPKFX]

Everyone seems to be ok with this and I have nothing to say either.
Once you rebase on master, I (or someone else) will merge.

[ratzlaff]

@tdesveauxPKFX rebased as requested!