+ifneq ($(wildcard $(BUILDDIR)/destinations),)
+# Get the output of the destination transform.
+override destinations := $(shell $(CAT) $(BUILDDIR)/destinations)
+
+# Pair source files and their destinations.
+override sourcedestinationpair := $(foreach destination,$(destinations),$(call sourcefile,$(firstword $(subst |, ,$(destination))))|$(call perdec,$(subst $(space),|,$(wordlist 2,$(words $(subst |, ,$(destination))),$(subst |, ,$(destination))))))
+
+# (callable) Get the destination for the given source files.
+override destination = $(foreach file,$1,$(patsubst $(file)|%,%,$(filter $(file)|%,$(sourcedestinationpair))))
+