libsepol: add missing dependency on host-flex

Fixes:

  http://autobuild.buildroot.net/results/580037bd376188e18a4a58927c929d21e9b2b03c/

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

package/libsepol/libsepol.mk

@@ -10,6 +10,7 @@ LIBSEPOL_LICENSE = LGPLv2.1+
 LIBSEPOL_LICENSE_FILES = COPYING
 
 LIBSEPOL_INSTALL_STAGING = YES
+LIBSEPOL_DEPENDENCIES = host-flex
 
 LIBSEPOL_MAKE_FLAGS = $(TARGET_CONFIGURE_OPTS)