pkgconfig module should have a way to exclude dependencies

[alanc]

Currently (meson 1.7) all dependencies used to build a library are output in either the Requires or Requires.private lines of the .pc file generated by the pkgconfig module. There should be some way to specify excluding dependencies that were only needed to build the library, but which aren't required by consumers of the library. For instance, the X11 libraries often depend on the *proto packages for the associated X11 extension protocol headers, but applications linking against those libraries don't need the protocol headers, since the library handles the protocol for them.

[alanc]

For now, the workaround is to not pass the library object to the pkgconfig module, but to instead specify all the fields manually in the pkg.generate call.