libdvdnav: requires pkg-config

Fixes
http://autobuild.buildroot.org/results/ababd836c7e7c3e63b3c7825244a56e30462c56d/build-end.log.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/libdvdnav/libdvdnav.mk

@@ -10,7 +10,7 @@ LIBDVDNAV_SITE = http://dvdnav.mplayerhq.hu/releases
 LIBDVDNAV_AUTORECONF = YES
 LIBDVDNAV_INSTALL_STAGING = YES
 
-LIBDVDNAV_DEPENDENCIES = libdvdread
+LIBDVDNAV_DEPENDENCIES = libdvdread host-pkg-config
 
 # By default libdvdnav tries to find dvdread-config in $PATH. Because
 # of cross compilation, we prefer using pkg-config.