Add test(s) for packages with autogen.sh

[stertooy]

Prompted by e1c51c7, which could have been caught earlier if there was a test for it.

We currently have a step that runs an autogen.sh script if it is present in the package. But neither ActionTestGAPDocPackage nor ActionTestOldDocPackage have such file, so it doesn't get tested.

[fingolfin]

Adding such a script (doing whatever) to one of these packages of course is trivial, but how do we "test" this?

One option would be that the dummy autogen.sh just does something like touch dummy_file && chmod a+x dummy_file, and the test consists of inspecting the content of the final tarball, to see if it contains that file, and is executable?

Actually, perhaps we should have a "manifest" with a precise list of all files that are supposed to be in the final tarball (possibly with info on whether they are executable or not), and we verify all of that? Then we also notice if a .aux file slips through, or if we discard something else, etc.