Spack-solvable versions, add tests to Spack workflow

[brenthuisman]

Changes

1. Spack interprets version info consisting of 2-tuples as ranges, leading to v0.8 being uninstallable if there has been a point release (v0.8.1).
2. Change Spack CI to use latest release and develop branch, because the former is how Arbor is rolled out in various centers, and thus should be verified to work, and the latter lets us know of upcoming issues with dependencies.
3. Changed Spack CI to not use build_spack_package.sh. This script does everything in /tmp, and Github Actions appear to be wiping /tmp between steps, which means breaking up the run into steps is difficult. Breaking up is desirable, because then one can see whether building or testing breaks.
4. Run Python tests after building the Spack package.
5. Also use Spack-provided deps when Spack is instructed to build master, not submodules.
6. Tiny fix for the ciwheelbuild failure.

Future issues

Out of scope for now, but identified as problems:

1. Currently, Spack cannot execute the unit tests, because the Google-Test package isn't built and Arbor doesn't look for it. @boeschf is looking at the latter: making it possible to build with an external Google Test.
   • Will be solved by Formal dependency version management #1731
2. The former is another problem: Spack does not or not always (it's not clear) concretize test dependencies. This is an open issue with low priority: spack install --test root not working properly in environment spack/spack#29447
   This mean that despite oru package.py properly including depends_on("[email protected]", type="test", when="@0.7.1:"), Spack does not build it, at least not in the dev-build workflow as we currently do. And it isn't clear what an always working workaround is, see issue. (Spack can't display the deps for the test variant: spack spec/solve include option for --test dependencies spack/spack#23586 spack spec -I arbor doesn't show Google Test, and neither does spack dependencies --deptype test arbor.)
   • Blocked by upstream.

[thorstenhater]

Great, some wording though (and I am scared of curl | bash)

[thorstenhater]

🎉

[thorstenhater]

👍