$(if $(word 2, $(KBUILD_EXTMOD)), \
$(error building multiple external modules is not supported))
+# Remove trailing slashes
+ifneq ($(filter %/, $(KBUILD_EXTMOD)),)
+KBUILD_EXTMOD := $(shell dirname $(KBUILD_EXTMOD).)
+endif
+
export KBUILD_EXTMOD
# Kbuild will save output files in the current working directory.