scripts: move DEFAULT_FEEDS definition to a separate file

modules.sh can't depend on openwrt/feeds.conf.default, otherwise the
initial update will fail.

scripts/default_feeds.sh

+DEFAULT_FEEDS="$(awk '{print $2}' openwrt/feeds.conf.default)"

scripts/feeds.sh

@@ -3,6 +3,7 @@
 set -e
 
 . scripts/modules.sh
+. scripts/default_feeds.sh
 
 
 rm -rf openwrt/tmp

scripts/modules.sh

@@ -2,7 +2,6 @@
 [ ! -f "$GLUON_SITEDIR"/modules ] || . "$GLUON_SITEDIR"/modules
 
 FEEDS="$(echo $GLUON_FEEDS $GLUON_SITE_FEEDS | tr ' ' '\n')"
-DEFAULT_FEEDS="$(awk '{print $2}' openwrt/feeds.conf.default)"
 
 GLUON_MODULES=openwrt
 

targets/generic

@@ -2,6 +2,7 @@
 
 
 . scripts/modules.sh
+. scripts/default_feeds.sh
 
 
 config "CONFIG_GLUON_SITEDIR=\"$GLUON_SITEDIR\""