`pkg-config` is a well established tool and all of our required
libraries do provide .pc files. Therefore let's declare `pkg-config` as
required and use it. In addition, remove now useless code.
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>