-ARCH_32 := $(filter-out %64, $(ARCHS))
-ARCH_64 := $(filter %64, $(ARCHS))
+# These are convenience functions for filtering based on substrings, as the
+# normal filter functions only accept one wildcard.
+FILTER_OUT_SUBSTRING=$(strip $(foreach string,$(2),$(if $(findstring $(1),$(string)),,$(string))))
+FILTER_SUBSTRING=$(strip $(foreach string,$(2),$(if $(findstring $(1),$(string)),$(string),)))
+
+ARCH_32:=$(call FILTER_OUT_SUBSTRING,64,$(ARCHS))
+ARCH_64:=$(call FILTER_SUBSTRING,64,$(ARCHS))