tools/perf/build: Invoke feature-checks 'clean' target from the main Makefile

config/Makefile is not included for the 'clean' target, so invoke the
config/feature-checks/Makefile 'clean' target from Makefile.perf.

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/n/tip-sh2cGvmsjbrazarlqre7pVwt@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

tools/perf/Makefile

@@ -809,7 +809,14 @@ $(INSTALL_DOC_TARGETS):
 
 ### Cleaning rules
 
-clean: $(LIBTRACEEVENT)-clean $(LIBLK)-clean
+#
+# This is here, not in config/Makefile, because config/Makefile does
+# not get included for the clean target:
+#
+config-clean:
+	@$(MAKE) -C config/feature-checks clean
+
+clean: $(LIBTRACEEVENT)-clean $(LIBLK)-clean config-clean
 	$(RM) $(LIB_OBJS) $(BUILTIN_OBJS) $(LIB_FILE) $(OUTPUT)perf-archive $(OUTPUT)perf.o $(LANG_BINDINGS)
 	$(RM) $(ALL_PROGRAMS) perf
 	$(RM) *.spec *.pyc *.pyo */*.pyc */*.pyo $(OUTPUT)common-cmds.h TAGS tags cscope*
@@ -829,6 +836,6 @@ else
     GIT-HEAD-PHONY =
 endif
 
-.PHONY: all install clean strip
+.PHONY: all install clean config-clean strip
 .PHONY: shell_compatibility_test please_set_SHELL_PATH_to_a_more_modern_shell
 .PHONY: $(GIT-HEAD-PHONY) TAGS tags cscope .FORCE-PERF-CFLAGS