perf tools: Pass build flags to traceevent build

So the extra user build flags are propagated to libtraceevent.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: "Herton R. Krzesinski" <herton@redhat.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Cc: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
Link: http://lkml.kernel.org/r/20181016150614.21260-3-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Makefile.perf

@@ -635,7 +635,7 @@ $(LIBPERF_IN): prepare FORCE
 $(LIB_FILE): $(LIBPERF_IN)
 	$(QUIET_AR)$(RM) $@ && $(AR) rcs $@ $(LIBPERF_IN) $(LIB_OBJS)
 
-LIBTRACEEVENT_FLAGS += plugin_dir=$(plugindir_SQ)
+LIBTRACEEVENT_FLAGS += plugin_dir=$(plugindir_SQ) 'EXTRA_CFLAGS=$(EXTRA_CFLAGS)' 'LDFLAGS=$(LDFLAGS)'
 
 $(LIBTRACEEVENT): FORCE
 	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) $(OUTPUT)libtraceevent.a