layer.conf: pick up bbappend files as well

conf/layer.conf

@@ -2,7 +2,7 @@
 BBPATH := "${LAYERDIR}:${BBPATH}"
 
 # We have a recipes directory, add to BBFILES
-BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb"
+BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"
 
 BBFILE_COLLECTIONS += "openembedded-layer"
 BBFILE_PATTERN_openembedded-layer := "^${LAYERDIR}/"