Add GHA workflow to exercise the existing tests

[arporter]

We already have test/Makefile. Therefore, this action needs to ensure a compiler is installed and then build all of the targets in that Makefile.
PSycloneBench can be used as a template for this:
https://github.com/stfc/PSycloneBench/blob/master/.github/workflows/makefile-test.yml

[arporter]

#4 has been merged.