Tune up GHA matrix

[jeking3]

• Add macos-15
• Move gcc-10+ to 22.04
• Move coverage from gcc-8 to gcc-13 and build with cxxstd 03,2b
• Move coverity to clang-12 and build with cxxstd 03,20
• Remove ubuntu-24.04 container, use 24.04 runner
• Remove redundant libc++ clang-12 build

I recently used these changes in dynamic_bitset.

[jeking3]

Hmm, since the build rules kick off a build for the push and for the CI, I canceled the push jobs. Those will appear skipped. This is because I named the branch as something that builds on commit, and I canceled the "push" actions job, leaving just the PR one.

[jeking3]

Interesting: moving clang-17 to use cxxstd=23 instead of cxxstd=2b caused a build failure.

[Flamefire]

Interesting: moving clang-17 to use cxxstd=23 instead of cxxstd=2b caused a build failure.

Odd indeed.

BTW: When intending to open a PR here consider renaming the branch first to something that doesn't trigger a build. fix/* is a pattern that triggers a build of the branch causing duplicate builds.

[jeking3]

Agreed, but too late for this series. I've just been canceling the push commit for now.

clang-17 is not compatible with libstdc++-13 from gcc in 2b/23 mode.
llvm/llvm-project#59827
I disabled building 2b/23 on clang-17 on 24.04 as it's not a libc++ test.

It was previously using a container, which was likely causing it to be a libc++ build and test, which was not the intention of that entry. Now that we're not using the container, it exposed this issue.

[Flamefire]

All good, GHA passed, won't wait for the other 2.

[Flamefire]

@jeking3

I tested a coverage job with GCC 13 instead of 8 with everything else equal and got quite a few changes in coverage:

  Lines        10353    10665     +312     
  + Hits          9920    10188     +268     
- Misses         433      477      +44     

One such change is a new, uncovered closing brace: https://app.codecov.io/gh/boostorg/nowide/pull/190/blob/include/boost/nowide/utf/convert.hpp#L91

That is even without branch coverage. Do you see such issues too?