tools: add a test for tool option parsing

tools: add a test for tool option parsing

We don't check for correctness in the output as such, just that whatever
combination of cmdline arguments still works/doesn't work. This is the
scaffolding and a few tests, but needs to be filled in, especially for
libinput measure and for some more complex combinations.

valgrind: requires one more python-related suppression
gitlab-ci: requires another environment variable so we know to skip the
	   --device tests (udev will time out on those)
meson: skip the test run in release builds, we pass the full path to the built
       libinput tool but rely on the subtool lookup that won't work in a
       release build

Fixes #174

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>