Add "make check" target

[fingolfin]

The virtual standard for invoking the test suite of make based build systems is make check. We also should support that. Multiple ways to do that:

• could be analias for e.g. testinstall
• could simply print a list of the actual test targets and what they do
• ...?

[ChrisJefferson]

Let's just link it to testinstall, that seems like a sensible value.

[fingolfin]

I made PR #3285 to resolve this, as I was again asked by people why make check does not work, and I agree that we should have it, as it is the "industry standard" and it makes sense to allow people to do things the "usual" way.

But I decided against making this an alias for make testinstall, as I never use make testinstall myself; for starters, it runs the suite twice, and thus takes twice longer; it creates log files I don't want; and worst of all, it does not set a proper exit code, so there is no good way to test programatically if the tests actually passed (yes, one can grep through the output; but note that I said "there is no good way", not: "there is now way" ;-).

So instead, I simply made make check run $(TESTGAP) tst/testinstall.g, which does the job nicely, and the resulting target description is much easier to understand than the code for the testinstall target.

[ChrisJefferson]

I agree with this. I also always run (on the command line) ./gap tst/testinstall.g, and tell others to do the same.