--- a/make/common/MakeBase.gmk	Mon Oct 23 10:41:34 2017 +0200
+++ b/make/common/MakeBase.gmk	Mon Oct 23 10:43:45 2017 +0200
@@ -737,6 +737,7 @@
 	$$($$(strip $4))
 
   $3 += $2
+  $3_SOURCES += $1
 endef
 
 # Returns the value of the first argument
@@ -749,6 +750,8 @@
 # Parameter 1 is the name of the rule. This name is used as variable prefix,
 # and the targets generated are listed in a variable by that name.
 #
+# The list of all source files is returned in $1_SOURCES.
+#
 # Remaining parameters are named arguments. These include:
 #   SRC     : Source root dir (defaults to dir of first file)
 #   DEST    : Dest root dir