LIBBPF = $(LIBBPF_PATH)libbpf.a
-BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
+BPFTOOL_VERSION ?= $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
$(LIBBPF): FORCE
$(if $(LIBBPF_OUTPUT),@mkdir -p $(LIBBPF_OUTPUT))