build: Don't dist generated files
Various generated files are ending up being disted, which is wrong becuase they leak the maintainer's prefix into the tarball and are generated anyway during build.
I was disting a custom tarball to include in Debian/Ubuntu (so we can have the CVE fixes since they aren't in a release yet, but that's by the by) and I noticed that my jhbuild prefix was included in them! I didn't really like that, so I had a look and it turns out that a few generated files were being included in the tarball (AFAICS) wrongly. Diffing shows no missing files, and the only difference is that the .pc files have changed versions, which is expected of course.
I might have missed some - these are just the ones that had the prefix leaked.