makefiles/modules.inc.mk: refactor, do not overwrite NO_PSEUDOMODULES

Refactor to define REALMODULES incrementally without overwriting
'NO_PSEUDOMODULES'.

This also allows an external makefile to maybe add something there if it really
needs to.

makefiles/modules.inc.mk

@@ -6,6 +6,6 @@ EXTDEFINES = $(addprefix -D,$(shell echo '$(ED)' | tr 'a-z-' 'A-Z_'))
 CFLAGS += $(EXTDEFINES)
 
 # filter "pseudomodules" from "real modules", but not "no_pseudomodules"
-NO_PSEUDOMODULES := $(filter $(NO_PSEUDOMODULES), $(_ALLMODULES))
-REALMODULES = $(filter-out $(PSEUDOMODULES), $(_ALLMODULES)) $(NO_PSEUDOMODULES)
+REALMODULES += $(filter-out $(PSEUDOMODULES), $(_ALLMODULES))
+REALMODULES += $(filter $(NO_PSEUDOMODULES), $(_ALLMODULES))
 BASELIBS += $(REALMODULES:%=$(BINDIR)/%.a)