iop: feeds_update: Generate list of feed-devices dirs

During feeds_update, generate a list of directories that contain
additional device profiles. Via some includes in the target image
Makefiles, any <BOARD/image/<SUBTARGET>.mk inside those directories will
get included, thus allowing to extend the list of devices from an
external feed. Motivation for this is that the external feed might have
a different access permission than the target-definition.

This code should probably live in the Perl script scripts/feeds in the
future, but for now, while we are experimenting with the feature, the
existing approach in feeds_update is considered good enough.

Signed-off-by: Andreas Gnau <andreas.gnau@iopsys.eu>

iop/scripts/feeds_update.sh

@@ -59,6 +59,12 @@ function feeds_update {
 	# record when we last run this script
 	touch tmp/.iop_bootstrap
 
+	(
+		echo '# DO NOT EDIT. Autogenerated file by ./iop feeds_update'
+		echo 'FEED_DEVICES_DIRS:='
+		find feeds -type f -name .is-feed-devices-dir -printf 'FEED_DEVICES_DIRS+=$(TOPDIR)/%h'
+	) > target/linux/feed-devices/feed-devices-list.mk
+
 	# always return true
 	exit 0
 }