build: Lua modules with multiple source files

modules/ketcd/ketcd.mk

+ketcd_SOURCES := ketcd.lua
 $(call make_lua_module,ketcd)

modules/modules.mk

@@ -24,9 +24,9 @@ endef
 
 # Lua target definition
 define lua_target
-$(1) := $(2)/$(1).lua
+$(1) := $$($(1)_SOURCES)
 $(1)-clean:
-$(1)-install: $(2)/$(1).lua
+$(1)-install: $$($(1)_SOURCES)
 	$(INSTALL) -d $(PREFIX)/$(MODULEDIR)
 	$(INSTALL) $$^ $(PREFIX)/$(MODULEDIR)
 .PHONY: $(1) $(1)-install $(1)-clean