xbps-src: added a new var for templates "dkms_modules".

It will be used by packages that will install DKMS modules.

xbps-src/shutils/metadata.sh

@@ -288,6 +288,13 @@ xbps_write_metadata_pkg_real()
 <key>long_desc</key>
 <string>$long_desc</string>
 _EOF
+	#
+	# If package sets $dkms_modules, add dkms rundep.
+	#
+	if [ -n "$dkms_modules" ]; then
+		Add_dependency run dkms
+	fi
+
 	#
 	# If package sets $openrc_services, add the OpenRC rundep.
 	#