perf tools: Enable libtraceevent dynamic linking

Currently we support only static linking with kernel's libtraceevent
(tools/lib/traceevent). This patch adds libtraceevent package detection
and support to link perf with it dynamically.

The libtraceevent package status is displayed with:
$ make VF=1 LIBTRACEEVENT_DYNAMIC=1
...
... libtraceevent: [ on ]

Default behavior remains the same (static linking).

Committer testing:

$ make LIBTRACEEVENT_DYNAMIC=1 VF=1 O=/tmp/build/perf -C tools/perf install-bin |& grep traceevent
Makefile.config:1090: *** Error: No libtraceevent devel library found, please install libtraceevent-devel. Stop.
$

Signed-off-by: Michael Petlan <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
LPU-Reference: [e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/build/Makefile.feature

···
         libpython-version               \
         libslang                        \
         libslang-include-subdir         \
+        libtraceevent                   \
         libcrypto                       \
         libunwind                       \
         pthread-attr-setaffinity-np     \

tools/build/feature/Makefile

···
          test-libpython-version.bin             \
          test-libslang.bin                      \
          test-libslang-include-subdir.bin       \
+         test-libtraceevent.bin                 \
          test-libcrypto.bin                     \
          test-libunwind.bin                     \
          test-libunwind-debug-frame.bin         \
···
 
 $(OUTPUT)test-libslang-include-subdir.bin:
 	$(BUILD) -lslang
+
+$(OUTPUT)test-libtraceevent.bin:
+	$(BUILD) -ltraceevent
 
 $(OUTPUT)test-libcrypto.bin:
 	$(BUILD) -lcrypto

tools/build/feature/test-libtraceevent.c

···
+// SPDX-License-Identifier: GPL-2.0
+#include <traceevent/trace-seq.h>
+
+int main(void)
+{
+	int rv = 0;
+	struct trace_seq s;
+	trace_seq_init(&s);
+	rv += !(s.state == TRACE_SEQ__GOOD);
+	trace_seq_destroy(&s);
+	return rv;
+}

tools/perf/Makefile.config

···
   endif
 endif
 
+ifdef LIBTRACEEVENT_DYNAMIC
+  $(call feature_check,libtraceevent)
+  ifeq ($(feature-libtraceevent), 1)
+    EXTLIBS += -ltraceevent
+  else
+    dummy := $(error Error: No libtraceevent devel library found, please install libtraceevent-devel);
+  endif
+endif
+
 # Among the variables below, these:
 #   perfexecdir
 #   perf_include_dir

tools/perf/Makefile.perf

···
 #
 # Define BUILD_BPF_SKEL to enable BPF skeletons
 #
+# Define LIBTRACEEVENT_DYNAMIC to enable libtraceevent dynamic linking
+#
 
 # As per kernel Makefile, avoid funny character set dependencies
 unexport LC_ALL
···
 
 LIBTRACEEVENT = $(TE_PATH)libtraceevent.a
 export LIBTRACEEVENT
-
 LIBTRACEEVENT_DYNAMIC_LIST = $(PLUGINS_PATH)libtraceevent-dynamic-list
 
 #
···
 
 export PERL_PATH
 
-PERFLIBS = $(LIBAPI) $(LIBTRACEEVENT) $(LIBSUBCMD) $(LIBPERF)
+PERFLIBS = $(LIBAPI) $(LIBSUBCMD) $(LIBPERF)
 ifndef NO_LIBBPF
   ifndef LIBBPF_DYNAMIC
     PERFLIBS += $(LIBBPF)
   endif
+endif
+ifndef LIBTRACEEVENT_DYNAMIC
+  PERFLIBS += $(LIBTRACEEVENT)
 endif
 
 # We choose to avoid "if .. else if .. else .. endif endif"