Try to fix macOS CI steps

[jkeuhlen]

This PR attempts to update our CI to fix a few issues.

Originally, I started off trying to fix the macOS failures, but that ended up leading me down a slightly different path. As is, I'd like to merge this anyways because I think it's an improvement, despite creating more failing tests than what we started with.

1. This expands LTS support beyond 19, showing real failures on more recent builds (nightly was already failing).
2. It skips builds on older LTS' on macOS due to architecture constraints (specifically LLVM compatibility issues).
3. It shows legitimate behavior failures on macOS, where openFileFromDir's masking behavior may be different from linux.
4. It also brings in the stack toolchain which apparently was required to get macOS ci running, despite working fine on the linux runners.