[rustbuild] Support `exclude` in config.toml, not just as a flag

[nagisa]

debuginfo-gdb tests fail on my system due to gdb not existing/gdb being misconfigured/gdb being not actually gdb/gdb being too new/gdb being too old/gdb outputting stuff to stderr/etc. There should be a way to disable selected collections of tests altogether in rustbuild.

I tried setting debuginfo-tests to false, but it only appears to tweak whether -g gets passed to the tests by default.

[Mark-Simulacrum]

So I think this is about making ./x.py test not run certain tests. Is that the correct interpretation, @nagisa? Or did you want something else?

[nagisa]

Certain groups of tests, as is stated in the original issue description.

[Mark-Simulacrum]

--exclude src/test/debuginfo would work today, though there's no way to put this in e.g. config.toml -- maybe it makes sense to add an exclude field to that?

[jyn514]

@nagisa is this still something you'd find useful? is --exclude enough, or would you use exclude in config.toml if we added support for that?

[nagisa]

exclude in config.toml would be stellar, but I can imagine myself living with just a flag (which I can write a wrapper script over for example)