tools/tracing: Use tools/build makefiles on latency-collector

Use tools/build/ makefiles to build latency-collector, inheriting
the benefits of it. For example: Before this patch, a missing
tracefs/traceevents headers will result in fail like this:

  ~/linux/tools/tracing/latency $ make
  cc -Wall -Wextra -g -O2  -o latency-collector latency-collector.c -lpthread
  latency-collector.c:26:10: fatal error: tracefs.h: No such file or directory
     26 | #include <tracefs.h>
        |          ^~~~~~~~~~~
  compilation terminated.
  make: *** [Makefile:14: latency-collector] Error 1

Which is not that helpful. After this change it reports:

  ~/linux/tools/tracing/latency# make

  Auto-detecting system features:
  ...                           libtraceevent: [ OFF ]
  ...                              libtracefs: [ OFF ]

  libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel
  libtracefs is missing. Please install libtracefs-dev/libtracefs-devel
  Makefile.config:29: *** Please, check the errors above..  Stop.

This type of output is common across other tools in tools/ like perf
and objtool.

Link: https://lkml.kernel.org/r/872420b0880b11304e4ba144a0086c6478c5b469.1710519524.git.bristot@kernel.org

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>

tools/tracing/latency/.gitignore

-# SPDX-License-Identifier: GPL-2.0
+# SPDX-License-Identifier: GPL-2.0-only
 latency-collector
+fixdep
+feature
+FEATURE-DUMP

tools/tracing/latency/Build

+latency-collector-y += latency-collector.o

tools/tracing/latency/Makefile

-# SPDX-License-Identifier: GPL-2.0
-# Makefile for vm tools
-#
-VAR_CFLAGS := $(shell pkg-config --cflags libtracefs 2>/dev/null)
-VAR_LDLIBS := $(shell pkg-config --libs libtracefs 2>/dev/null)
+# SPDX-License-Identifier: GPL-2.0-only
 
-TARGETS = latency-collector
-CFLAGS = -Wall -Wextra -g -O2 $(VAR_CFLAGS)
-LDFLAGS = -lpthread $(VAR_LDLIBS)
+ifeq ($(srctree),)
+  srctree	:= $(patsubst %/,%,$(dir $(CURDIR)))
+  srctree	:= $(patsubst %/,%,$(dir $(srctree)))
+  srctree	:= $(patsubst %/,%,$(dir $(srctree)))
+endif
 
-all: $(TARGETS)
+include $(srctree)/tools/scripts/Makefile.include
 
-%: %.c
-	$(CC) $(CFLAGS) -o $@ $< $(LDFLAGS)
+# O is an alias for OUTPUT
+OUTPUT		:= $(O)
 
-clean:
-	$(RM) latency-collector
+ifeq ($(OUTPUT),)
+  OUTPUT	:= $(CURDIR)
+else
+  # subdir is used by the ../Makefile in $(call descend,)
+  ifneq ($(subdir),)
+    OUTPUT	:= $(OUTPUT)/$(subdir)
+  endif
+endif
+
+ifneq ($(patsubst %/,,$(lastword $(OUTPUT))),)
+  OUTPUT	:= $(OUTPUT)/
+endif
+
+LATENCY-COLLECTOR	:= $(OUTPUT)latency-collector
+LATENCY-COLLECTOR_IN	:= $(LATENCY-COLLECTOR)-in.o
+
+export CC	:= gcc
+export LD	:= ld
+export AR	:= ar
+export PKG_CONFIG := pkg-config
+
+FEATURE_TESTS	:= libtraceevent
+FEATURE_TESTS	+= libtracefs
+FEATURE_DISPLAY	:= libtraceevent
+FEATURE_DISPLAY	+= libtracefs
+
+ifeq ($(V),1)
+  Q 		=
+else
+  Q 		= @
+endif
+
+all: $(LATENCY-COLLECTOR)
+
+include $(srctree)/tools/build/Makefile.include
+
+# check for dependencies only on required targets
+NON_CONFIG_TARGETS := clean install
 
-prefix ?= /usr/local
-sbindir ?= ${prefix}/sbin
+config		:= 1
+ifdef MAKECMDGOALS
+ifeq ($(filter-out $(NON_CONFIG_TARGETS),$(MAKECMDGOALS)),)
+ config		:= 0
+endif
+endif
 
-install: all
-	install -d $(DESTDIR)$(sbindir)
-	install -m 755 -p $(TARGETS) $(DESTDIR)$(sbindir)
+ifeq ($(config),1)
+  include $(srctree)/tools/build/Makefile.feature
+  include Makefile.config
+endif
+
+CFLAGS		+= $(INCLUDES) $(LIB_INCLUDES)
+
+export CFLAGS OUTPUT srctree
+
+$(LATENCY-COLLECTOR): $(LATENCY-COLLECTOR_IN)
+	$(QUIET_LINK)$(CC) $(LDFLAGS) -o $(LATENCY-COLLECTOR) $(LATENCY-COLLECTOR_IN) $(EXTLIBS)
+
+latency-collector.%: fixdep FORCE
+	make -f $(srctree)/tools/build/Makefile.build dir=. $@
+
+$(LATENCY-COLLECTOR_IN): fixdep FORCE
+	make $(build)=latency-collector
+
+INSTALL		:= install
+MKDIR		:= mkdir
+STRIP		:= strip
+BINDIR		:= /usr/bin
+
+install:
+	@$(MKDIR) -p $(DESTDIR)$(BINDIR)
+	$(call QUIET_INSTALL,latency-collector)$(INSTALL) $(LATENCY-COLLECTOR) -m 755 $(DESTDIR)$(BINDIR)
+	@$(STRIP) $(DESTDIR)$(BINDIR)/latency-collector
+
+clean:
+	$(call QUIET_CLEAN, latency-collector)
+	$(Q)find . -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
+	$(Q)@rm -f latency-collector fixdep FEATURE-DUMP
+	$(Q)rm -rf feature
+.PHONY: FORCE clean install

tools/tracing/latency/Makefile.config

+# SPDX-License-Identifier: GPL-2.0-only
+
+STOP_ERROR :=
+
+define lib_setup
+  $(eval EXTLIBS += -l$(1))
+  $(eval LIB_INCLUDES += $(shell sh -c "$(PKG_CONFIG) --cflags lib$(1)"))
+endef
+
+$(call feature_check,libtraceevent)
+ifeq ($(feature-libtraceevent), 1)
+  $(call detected,CONFIG_LIBTRACEEVENT)
+  $(call lib_setup,traceevent)
+else
+  STOP_ERROR := 1
+  $(info libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel)
+endif
+
+$(call feature_check,libtracefs)
+ifeq ($(feature-libtracefs), 1)
+  $(call detected,CONFIG_LIBTRACEFS)
+  $(call lib_setup,tracefs)
+else
+  STOP_ERROR := 1
+  $(info libtracefs is missing. Please install libtracefs-dev/libtracefs-devel)
+endif
+
+ifeq ($(STOP_ERROR),1)
+  $(error Please, check the errors above.)
+endif