Using Make to run tests and test T14999

Test T14999 is skipped:

./hadrian/build -j --flavour=devel2 --freeze1 test --only=T14999

It is marked as unless(... have_gdb() and have_readelf(), skip). But I do have gdb and readelf. So what's going on?

The only place where we detect gdb and readelf is in test.mk

ifeq "$(HAVE_READELF)" "YES"
RUNTEST_OPTS += -e config.have_readelf=True
else
RUNTEST_OPTS += -e config.have_readelf=False
endif

Looks like this was not ported to Hadrian. Using the old method make test TEST=T14999 works (although it tries to use my local ghc instead of the one in _build).

The good news is that T14999 is the only test using either have_gdb() or have_readelf(). The bad news is that there is plenty of other logic in test.mk and I'm not sure what else is missing.

Proposal:

1. Port all logic initializing RUNTEST_OPTS to Hadrian.

2. Remove the test target from Makefile. The Python testdriver can call Make (makefile_test) but Make shouldn't be calling Python. I see that we still use Make in .gitlab-ci.yml: make -Ctestsuite list_broken TEST_HC=$GHC, this would have to be changed. Is Make used anywhere else?

3. The test runner initializes configuration to dummy values config.have_readelf=False https://gitlab.haskell.org/ghc/ghc/-/blob/257f1567395be441ebf7ada996e4edf36abbe7e9/testsuite/driver/testglobals.py#L172. IMO, we should avoid this as much as possible - if a parameter wasn't passed, the test runner should crash. Otherwise tests can get silently skipped like in this case.