perf build: Use pkg-config for feature check for libtrace{event,fs}

Needed to add required include directories for the feature detection
to succeed. The header tracefs.h is installed either into the include
directory /usr/include/tracefs/tracefs.h when using the Makefile, or
into /usr/include/libtracefs/tracefs.h when using meson to build
libtracefs. The header tracefs.h uses #include <event-parse.h> from
libtraceevent, so pkg-config needs to pick the correct include directory
for libtracefs and add the one for libtraceevent to succeed.

Note that in baa2ca59 the variable
LIBTRACEEVENT_DIR was introduced, and now the method to compile against
non-standard locations requires PKG_CONFIG_PATH to be set instead, which
works for both libtraceevent and libtracefs.
Signed-off-by: Guilherme Amadio <amadio@gentoo.org>
Reviewed-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240606153625.2255470-2-amadio@gentoo.org

tools/build/feature/test-libtracefs.c

 // SPDX-License-Identifier: GPL-2.0
-#include <tracefs/tracefs.h>
+#include <tracefs.h>
 
 int main(void)
 {

tools/perf/Makefile.config

@@ -183,14 +183,12 @@ FEATURE_CHECK_CFLAGS-libzstd := $(LIBZSTD_CFLAGS)
 FEATURE_CHECK_LDFLAGS-libzstd := $(LIBZSTD_LDFLAGS)
 
 # for linking with debug library, run like:
-# make DEBUG=1 LIBTRACEEVENT_DIR=/opt/libtraceevent/
-TRACEEVENTLIBS := -ltraceevent
-ifdef LIBTRACEEVENT_DIR
-  LIBTRACEEVENT_CFLAGS  := -I$(LIBTRACEEVENT_DIR)/include
-  LIBTRACEEVENT_LDFLAGS := -L$(LIBTRACEEVENT_DIR)/lib
-endif
-FEATURE_CHECK_CFLAGS-libtraceevent := $(LIBTRACEEVENT_CFLAGS)
-FEATURE_CHECK_LDFLAGS-libtraceevent := $(LIBTRACEEVENT_LDFLAGS) $(TRACEEVENTLIBS)
+# make DEBUG=1 PKG_CONFIG_PATH=/opt/libtraceevent/(lib|lib64)/pkgconfig
+FEATURE_CHECK_CFLAGS-libtraceevent := $(shell $(PKG_CONFIG) --cflags libtraceevent)
+FEATURE_CHECK_LDFLAGS-libtraceevent := $(shell $(PKG_CONFIG) --libs libtraceevent)
+
+FEATURE_CHECK_CFLAGS-libtracefs := $(shell $(PKG_CONFIG) --cflags libtracefs)
+FEATURE_CHECK_LDFLAGS-libtracefs := $(shell $(PKG_CONFIG) --libs libtracefs)
 
 FEATURE_CHECK_CFLAGS-bpf = -I. -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(SRCARCH)/include/uapi -I$(srctree)/tools/include/uapi
 # include ARCH specific config
@@ -1178,10 +1176,10 @@ endif
 ifneq ($(NO_LIBTRACEEVENT),1)
   $(call feature_check,libtraceevent)
   ifeq ($(feature-libtraceevent), 1)
-    CFLAGS += -DHAVE_LIBTRACEEVENT $(LIBTRACEEVENT_CFLAGS)
-    LDFLAGS += $(LIBTRACEEVENT_LDFLAGS)
-    EXTLIBS += ${TRACEEVENTLIBS}
-    LIBTRACEEVENT_VERSION := $(shell PKG_CONFIG_PATH=$(LIBTRACEEVENT_DIR) $(PKG_CONFIG) --modversion libtraceevent)
+    CFLAGS += -DHAVE_LIBTRACEEVENT
+    LDFLAGS += $(shell $(PKG_CONFIG) --libs-only-L libtraceevent)
+    EXTLIBS += $(shell $(PKG_CONFIG) --libs-only-l libtraceevent)
+    LIBTRACEEVENT_VERSION := $(shell $(PKG_CONFIG) --modversion libtraceevent)
     LIBTRACEEVENT_VERSION_1 := $(word 1, $(subst ., ,$(LIBTRACEEVENT_VERSION)))
     LIBTRACEEVENT_VERSION_2 := $(word 2, $(subst ., ,$(LIBTRACEEVENT_VERSION)))
     LIBTRACEEVENT_VERSION_3 := $(word 3, $(subst ., ,$(LIBTRACEEVENT_VERSION)))
@@ -1194,7 +1192,9 @@ ifneq ($(NO_LIBTRACEEVENT),1)
 
   $(call feature_check,libtracefs)
   ifeq ($(feature-libtracefs), 1)
-    EXTLIBS += -ltracefs
+    CFLAGS +=  $(shell $(PKG_CONFIG) --cflags libtracefs)
+    LDFLAGS += $(shell $(PKG_CONFIG) --libs-only-L libtracefs)
+    EXTLIBS += $(shell $(PKG_CONFIG) --libs-only-l libtracefs)
     LIBTRACEFS_VERSION := $(shell $(PKG_CONFIG) --modversion libtracefs)
     LIBTRACEFS_VERSION_1 := $(word 1, $(subst ., ,$(LIBTRACEFS_VERSION)))
     LIBTRACEFS_VERSION_2 := $(word 2, $(subst ., ,$(LIBTRACEFS_VERSION)))
@@ -1315,7 +1315,6 @@ ifeq ($(VF),1)
   $(call print_var,LIBUNWIND_DIR)
   $(call print_var,LIBDW_DIR)
   $(call print_var,JDIR)
-  $(call print_var,LIBTRACEEVENT_DIR)
 
   ifeq ($(dwarf-post-unwind),1)
     $(call feature_print_text,"DWARF post unwind library", $(dwarf-post-unwind-text)) $(info $(MSG))