-cpp-srcs-left = $(lib)-routines
-ifneq (,$($(lib)-routines))
-cpp-srcs-left = $($(lib)-routines)
-include $(patsubst %,$(..)cppflags-iterator.mk,$($(lib)-routines))
-endif
-ifneq (,$($(lib)-sysdep_routines))
-cpp-srcs-left = $($(lib)-sysdep_routines)
-include $(patsubst %,$(..)cppflags-iterator.mk,$($(lib)-sysdep_routines))
+# This will define `libof-ROUTINE := LIB' for each of the routines.
+cpp-srcs-left := $($(lib)-routines) $($(lib)-sysdep_routines)
+ifneq (,$(cpp-srcs-left))
+include $(patsubst %,$(..)libof-iterator.mk,$(cpp-srcs-left))