build: allow overriding the base feed list

Makefile

@@ -46,10 +46,16 @@ $(eval $(call mkabspath,GLUON_PATCHESDIR))
 GLUON_MULTIDOMAIN ?= 0
 GLUON_DEBUG ?= 0
 
+# Can be overridden via environment/command line/... to use the Gluon
+# build system for non-Gluon builds
+define GLUON_BASE_FEEDS ?=
+src-link gluon_base ../../package
+endef
+
 GLUON_VARS = \
 	GLUON_RELEASE GLUON_REGION GLUON_MULTIDOMAIN GLUON_DEBUG GLUON_DEPRECATED GLUON_DEVICES \
 	GLUON_TARGETSDIR GLUON_PATCHESDIR GLUON_TMPDIR GLUON_IMAGEDIR GLUON_PACKAGEDIR \
-	GLUON_SITEDIR GLUON_RELEASE GLUON_BRANCH GLUON_LANGS BOARD SUBTARGET
+	GLUON_SITEDIR GLUON_RELEASE GLUON_BRANCH GLUON_LANGS GLUON_BASE_FEEDS BOARD SUBTARGET
 
 unexport $(GLUON_VARS)
 GLUON_ENV = $(foreach var,$(GLUON_VARS),$(var)=$(call escape,$($(var))))

scripts/feeds.sh

@@ -11,7 +11,7 @@ rm -rf openwrt/feeds
 rm -rf openwrt/package/feeds
 
 (
-	echo 'src-link gluon_base ../../package'
+	echo "$GLUON_BASE_FEEDS"
 	for feed in $FEEDS; do
 		echo "src-link $feed ../../packages/$feed"
 	done