this is a bug in old addons, just comment every line that looks like:
ADDON_DEPENDENCIES =
ADDON_CFLAGS =
...to look like:
# ADDON_DEPENDENCIES =
# ADDON_CFLAGS =
...the way we parse the addon_config.mk now is by overwritting any value from parsing the file system if we encounter any = and adding to it if we find += so those lines are making the parser not include any library, source...
the makefiles should be doing the same actually so not sure why it might be working there but it shouldn't : )