[PATCH v2] perf/build: fix broken dependency check for libtracefs

[Thomas Richter]

Perf build 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
 #

Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>
Cc: jolsa@xxxxxxxxxx
Cc: rostedt@xxxxxxxxxxx
---
 tools/build/feature/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index 0f0aa9b7d7b5..2cd6dbbee088 100644
--- a/tools/build/feature/Makefile
+++ b/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
-- 
2.41.0