perf build: Fix broken feature check for libtracefs due to external lib changes

The perf build process auto-detects features and packages already
installed for its build. This is done in directory tools/build/feature.
This directory contains small sample programs. When they successfully
compile the necessary prereqs in form of libraries and header files are
present.

Such a check is also done for libtracefs. And this check fails:

Output before:
 # rm -f test-libtracefs.bin; make test-libtracefs.bin
 gcc  -MD -Wall -Werror -o test-libtracefs.bin test-libtracefs.c \
	 > test-libtracefs.make.output 2>&1 -ltracefs
 make: *** [Makefile:211: test-libtracefs.bin] Error 1
 # cat test-libtracefs.make.output
 In file included from test-libtracefs.c:2:
 /usr/include/tracefs/tracefs.h:11:10: fatal error: \
	 event-parse.h: No such file or directory
   11 | #include <event-parse.h>
      |          ^~~~~~~~~~~~~~~
 compilation terminated.
 #

The root cause of this compile error is commit 880885d9c22e
("libtracefs: Remove "traceevent/" from referencing libtraceevent
headers") in the libtracefs project hosted here:
https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/

That mentioned patch removes the traceevent/ directory name from
the include statement, causing the file not to be included even
when the libtraceevent-devel package is installed. This package contains
the file referred to in tracefs/tracefs.h:

 # rpm -ql libtraceevent-devel
 /usr/include/traceevent
 /usr/include/traceevent/event-parse.h  <----- here
 /usr/include/traceevent/event-utils.h
 /usr/include/traceevent/kbuffer.h
 /usr/include/traceevent/trace-seq.h
 /usr/lib64/libtraceevent.so
 /usr/lib64/pkgconfig/libtraceevent.pc
 #

With this patch the compile succeeds.

Output after:
 # rm -f test-libtracefs.bin; make test-libtracefs.bin
 gcc  -MD -Wall -Werror -o test-libtracefs.bin test-libtracefs.c \
	 > test-libtracefs.make.output 2>&1 -I/usr/include/traceevent -ltracefs
 #

Committer testing:

  $ make -k BUILD_BPF_SKEL=1 CORESIGHT=1 O=/tmp/build/perf-tools -C tools/perf install-bin

Before:

  $ cat /tmp/build/perf-tools/feature/test-libtracefs.make.output
  In file included from test-libtracefs.c:2:
  /usr/include/tracefs/tracefs.h:11:10: fatal error: event-parse.h: No such file or directory
     11 | #include <event-parse.h>
        |          ^~~~~~~~~~~~~~~
  compilation terminated.
  $
  $ grep -i tracefs /tmp/build/perf-tools/FEATURE-DUMP
  feature-libtracefs=0
  $

After:

  $ cat /tmp/build/perf-tools/feature/test-libtracefs.make.output
  $
  $ grep -i tracefs /tmp/build/perf-tools/FEATURE-DUMP
  feature-libtracefs=1
  $

Signed-off-by: Thomas Richter <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Steven Rostedt (VMware) <[email protected]>
Cc: Sumanth Korikkar <[email protected]>
Cc: Sven Schnelle <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: Thomas Richter

tools/build/feature/Makefile

@@ -208,7 +208,7 @@ $(OUTPUT)test-libtraceevent.bin:
 	$(BUILD) -ltraceevent
 
 $(OUTPUT)test-libtracefs.bin:
-	$(BUILD) -ltracefs
+	 $(BUILD) $(shell $(PKG_CONFIG) --cflags libtraceevent 2>/dev/null) -ltracefs
 
 $(OUTPUT)test-libcrypto.bin:
 	$(BUILD) -lcrypto