tools: bpftool: don't pass FEATURES_DUMP to libbpf

bpftool does not export features it probed for, i.e.
FEATURE_DUMP_EXPORT is always empty, so don't try to communicate
the features to libbpf.  It has no effect.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/bpf/bpftool/Makefile

@@ -26,7 +26,7 @@ LIBBPF = $(BPF_PATH)libbpf.a
 BPFTOOL_VERSION := $(shell make --no-print-directory -sC ../../.. kernelversion)
 
 $(LIBBPF): FORCE
-	$(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(OUTPUT) $(OUTPUT)libbpf.a FEATURES_DUMP=$(FEATURE_DUMP_EXPORT)
+	$(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(OUTPUT) $(OUTPUT)libbpf.a
 
 $(LIBBPF)-clean:
 	$(call QUIET_CLEAN, libbpf)