Teach gather_port_vars about subpackages

[kprovost]

List subpackages in addition to the parent package if the origin specifies a subpackage.

This fixes pkgclean, which would otherwise remove subpackages even if they're explicitly listed in the to-keep file.

[bdrewery]

Did you run the test suite? make -j2 check

[kprovost]

The test suite produces a number of failures for me, even without this patch.
With it there's one extra failure in pkgqueue_basic.sh:

[00:00:00] (00:00:00) stderr: HAVE:
[00:00:00] (00:00:00) stderr:      1    build:pkg build:bash$
[00:00:00] (00:00:00) stderr:      2    build:pkg build:patchutils$
[00:00:00] (00:00:00) stderr:      3    build:bash build:patchutils$
[00:00:00] (00:00:00) stderr: EXPECTED:
[00:00:00] (00:00:00) stderr:      1    build:pkg build:bash$
[00:00:00] (00:00:00) stderr:      2    build:bash build:patchutils$
[00:00:00] (00:00:00) stderr:      3    build:pkg build:patchutils$
[00:00:00] (00:00:00) stderr: --- /tmp/poudriere/test/tmp.AZ2Qyrk92K/assert_file.expected.99cK4Hgl8p^I2025-04-30 15:41:14.905710000 +0200$
[00:00:00] (00:00:00) stderr: +++ /tmp/poudriere/test/tmp.AZ2Qyrk92K/assert_out.gyxyAzwHY7^I2025-04-30 15:41:14.897019000 +0200$
[00:00:00] (00:00:00) stderr: @@ -1,3 +1,3 @@$
[00:00:00] (00:00:00) stderr:  build:pkg build:bash$
[00:00:00] (00:00:00) stderr: -build:bash build:patchutils$
[00:00:00] (00:00:00) stderr:  build:pkg build:patchutils$
[00:00:00] (00:00:00) stderr: +build:bash build:patchutils$
[00:00:00] (00:00:00) stderr: =>> Cleaning up

It's not clear to me if that's a real problem or just a flaky test. I'd certainly not expect my patch to re-order things, at least not as long as no sub packages are involved.

[bdrewery]

Which commit hash are you testing on?

[kprovost]

b3127a3

[kprovost]

Is there anything I can/need to do to push this forward?

[bdrewery]

I need to find time to integrate it with extra tests I have for subpackages. I'm sure this fixes something, but it's a complex feature. As is incremental is completely broken with subpackages. So I am cautious about introducing more change to it. I'll try to find time in the next few weeks to bring in your PR.