perf: Build with make -C <Linux O=...>

[Andy Shevchenko]

My setup includes Linux kernel repository and Buildroot.
I build Linux kernel with make O=<Linux O=...> and then
when I try to build perf by running

	make -j1 V=1 JOBS=1 \
		-C <Linux O=...> \
		CROSS_COMPILE=".../i586-buildroot-linux-uclibc-" \
		DESTDIR="..." tools/perf_install

where <Linux O=...> is a patch to output folder of built Linux kernel,
I got wrong path in perf during build, so, instead of tools/perf it becomes
tools/perf/tools/perf.

Note, it fulfills my purposes with minimal features supported,
that's why not every library got "fixed".

Below is the patch which helped me to achieve above.

I'm pretty sure it's not the best solution. Anyway, would like to hear any
ideas how to do this better.

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 4d46ca6d7e20..c56d4c0fd29b 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -698,23 +698,24 @@ $(LIBPERF_A): $(LIBPERF_IN)
 LIBTRACEEVENT_FLAGS += plugin_dir=$(plugindir_SQ) 'EXTRA_CFLAGS=$(EXTRA_CFLAGS)' 'LDFLAGS=$(LDFLAGS)'
 
 $(LIBTRACEEVENT): FORCE
-	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) $(OUTPUT)libtraceevent.a
+	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) subdir= $(OUTPUT)libtraceevent.a
 
 libtraceevent_plugins: FORCE
-	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) plugins
+	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) subdir= plugins
 
 $(LIBTRACEEVENT_DYNAMIC_LIST): libtraceevent_plugins
-	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) $(OUTPUT)libtraceevent-dynamic-list
+	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) subdir= $(OUTPUT)libtraceevent-dynamic-list
 
 $(LIBTRACEEVENT)-clean:
 	$(call QUIET_CLEAN, libtraceevent)
 	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) O=$(OUTPUT) clean >/dev/null
 
 install-traceevent-plugins: libtraceevent_plugins
-	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) install_plugins
+	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) subdir= install_plugins
 
 $(LIBAPI): FORCE
-	$(Q)$(MAKE) -C $(LIB_DIR) O=$(OUTPUT) $(OUTPUT)libapi.a
+	$(Q)$(MAKE) -C $(LIB_DIR) O=$(OUTPUT) subdir= $(OUTPUT)libapi.a
+	mkdir -p $(API_PATH) && cp $(OUTPUT)libapi.a $(LIBAPI)
 
 $(LIBAPI)-clean:
 	$(call QUIET_CLEAN, libapi)
@@ -728,7 +729,7 @@ $(LIBBPF)-clean:
 	$(Q)$(MAKE) -C $(BPF_DIR) O=$(OUTPUT) clean >/dev/null
 
 $(LIBSUBCMD): FORCE
-	$(Q)$(MAKE) -C $(SUBCMD_DIR) O=$(OUTPUT) $(OUTPUT)libsubcmd.a
+	$(Q)$(MAKE) -C $(SUBCMD_DIR) O=$(OUTPUT) subdir= $(OUTPUT)libsubcmd.a
 
 $(LIBSUBCMD)-clean:
 	$(call QUIET_CLEAN, libsubcmd)
-- 
2.20.1