Makefile improvements

[jix]

Several makefile improvements

• Updates make help text which was outdated
• Renames the test target to make test
• Make make ci error without either cad suite installed (points to make test and allows overriding with make run_ci)
• Also check for auxiliary tools (btorsim for btor and yices for abc/aiger) when determining which tests can be run with the available tools
• Automatically rerun test_rules.py when running make test after the set of available tools changed

This should fix everything related to the tests / makefile mentioned in #160

[nakengelhardt]

Sweet! Could you also make the check for btorsim check that it's a version that supports the --vcd argument?

[jix]

Now it also checks that btorsim supports the --vcd option. With more complex checks for the available tools now, I also added an option to fail on any skipped tests and enabled that for CI, so we don't accidentally stop running any tests because the detection broke.