All code is built as C++ via CXX, but we still have some references to
CC. Trying to make sure we don't add plain C later by hiding the C
compiler. (So it's always enough to override CXX=... in configure)
Add an explicit 'sha' parameter to reusable-build, to define which
commit to build. This will be needed for PR coverage jobs. Consequently
use the 'archive' output from reusable-build to simplify retrieving the
resulting artifact in dependent jobs. Also fetch full history in
coverage builds.
Chores:
- Remove ci-ccache-maint. This has never been useful and is just cruft.
- Remove then unused CI_COMMIT
- Change job names so they come out nicer in the web views
- Make os-name input to reusable-build always explicit
Improvements:
- Have at most build-test job in progress per branch
- Cancel in-progress build-test jobs on PRs
- In forks (that is, not on 'verilator/verilator'), cancel any
in-progress build-test jobs on push to the branch