libmatroska: add host-pkgconf dependency

libmatroska configure.ac uses PKG_CHECK_MODULES(), so this package
needs to depend on host-pkgconf.

Fixes:

  http://autobuild.buildroot.org/results/80a/80a9f0f5594ab833600ea8514dc184e50d2bf08c/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libmatroska/libmatroska.mk

@@ -10,6 +10,6 @@ LIBMATROSKA_SITE = http://dl.matroska.org/downloads/libmatroska
 LIBMATROSKA_INSTALL_STAGING = YES
 LIBMATROSKA_LICENSE = LGPLv2.1+
 LIBMATROSKA_LICENSE_FILES = LICENSE.LGPL
-LIBMATROSKA_DEPENDENCIES = libebml
+LIBMATROSKA_DEPENDENCIES = libebml host-pkgconf
 
 $(eval $(autotools-package))