package: Ensure pclist files are deterministic and don't use full paths

Currently the pkgconfig pclist files contain full paths which are build
host specific and the order of entries is not deterministic.

Fix both these issues so the files are deterministic.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit e422e29b)
Signed-off-by: Steve Sakoman <steve@sakoman.com>