configure.ac: add missing call to PKG_PROG_PKG_CONFIG
configure.ac: add missing call to PKG_PROG_PKG_CONFIG

Without the call to PKG_PROG_PKG_CONFIG, the calls to PKG_CHECK_MODULES
do not work properly.

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

nicolasvasilache/ppcg,Meinersbur/ppcg,Meinersbur/ppcg,nicolasvasilache/ppcg