[CI] Run tests on GitHub Actions

[giordano]

The general notion is that the tests of this package would take a long time without persistent caching, and would also require a large amount of storage available. Let's test how bad things are nowadays.

[giordano]

  Unable to automatically download/install artifact 'GCCBootstrap-x86_64-linux-musl.v9.1.0.x86_64-linux-musl.unpacked' from sources listed in '/home/runner/.julia/packages/BinaryBuilderBase/yt9V4/Artifacts.toml'.
  Sources attempted:
  - https://pkg.julialang.org/artifact/13a1bcd3a29ff96c26935ddcea9aeb149ad49451
      Error: AssertionError: size == padded_size == 0
  This error may be a symptom of insufficient disk space on the device the tarball is being written to.
  
  - https://github.com/JuliaPackaging/Yggdrasil/releases/download/GCCBootstrap-v9.1.0+3/GCCBootstrap-x86_64-linux-musl.v9.1.0.x86_64-linux-musl.unpacked.tar.gz
      Error: AssertionError: size == padded_size == 0
  This error may be a symptom of insufficient disk space on the device the tarball is being written to.

despite having 49 GB available at the beginning, sigh.

[giordano]

The job with squashfs images was actually successful (and in ~40 minutes, not horrible), but used about 42 GB in the process. The jobs with uncompressed toolchains failed at some point because of not enough space.

I guess this was worth a try at least to know what's the situation.