Install working pkgconfig .pc files for compat libraries

[arichardson]

Summary

Instead of installing them to /usr/libdata/pkgconfig, we use
/usr/lib<suffix>/pkgconfig. I'm not sure why native ABI libdirs are
installed to /usr/libdata/pkgconfig instead of /usr/lib/pkgconfig, but
I don't think this commit should change that.

Test Plan

grep -rn libdir= ./usr/lib32/pkgconfig/*.pc

[imp]

A quick glance says "this looks good to me" if that's the feedback you're looking for :)

[arichardson]

Use FreeBSD HEAD instead of CheriBSD HEAD as the base

[arichardson]

In D34939#792003, @imp wrote:

A quick glance says "this looks good to me" if that's the feedback you're looking for :)

Thanks, yes that is what I was looking for before updating the review :)

[arichardson]

Ping? Is this ok to commit?

[bapt]

It's a pitty we can't be consistent and have a libdata equivalent for compat libraries, but on the other hand I don't have better proposal that what is proposed here.

[arichardson]

If there are no further comments/suggestions, I'll commit this next week (most likely Wednesday)