Aiden Woodruff

Using ccache will also help

It's been a few years since I used the GitHub actions ccache features, but I think the usual approach is to load the cache as an artifact before building and...

We can also make better use of the `on.*.paths`/`on.*.paths-ignore` key to avoid running CI for documentation-only updates. The only thing there is to make sure that `.github/workflows` is in there...

There is a guide on ccache here: https://cristianadam.eu/20200113/speeding-up-c-plus-plus-github-actions-using-ccache/ There might be a storage tradeoff/consideration, especially since our builds tend to be large.

Working on #500 to add ccache, but we should also look at pruning the run matrix. Specifically: - Do we need to run clang/gcc for every combination? Or only for...

Is this about what we want? Not sure when we do want them. ``` exclude: - compiler: { name: LLVM } build_type: Release - cxx_standard: 20 build_type: Release ```

@flagdanger can this be closed now that #433 is merged?