perf bpf-event: Use libbpf version rather than feature check

The feature check guarded the -DHAVE_LIBBPF_STRINGS_SUPPORT is
unnecessary as it is sufficient and easier to use the
LIBBPF_CURRENT_VERSION_GEQ macro.

Signed-off-by: Ian Rogers <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Blake Jones <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Makefile.config

···
 	  LIBBPF_INCLUDE = $(LIBBPF_DIR)/..
         endif
       endif
-
-      FEATURE_CHECK_CFLAGS-libbpf-strings="-I$(LIBBPF_INCLUDE)"
-      $(call feature_check,libbpf-strings)
-      ifeq ($(feature-libbpf-strings), 1)
-        $(call detected,CONFIG_LIBBPF_STRINGS)
-        CFLAGS += -DHAVE_LIBBPF_STRINGS_SUPPORT
-      endif
     endif
   endif # NO_LIBBPF
 endif # NO_LIBELF

tools/perf/builtin-check.c

···
 // SPDX-License-Identifier: GPL-2.0
 #include "builtin.h"
 #include "color.h"
+#include "util/bpf-utils.h"
 #include "util/debug.h"
 #include "util/header.h"
 #include <tools/config.h>

tools/perf/util/bpf-event.c

···
 		.sz = sizeof(struct btf_dump_type_data_opts),
 		.skip_names = 1,
 		.compact = 1,
-#if LIBBPF_CURRENT_VERSION_GEQ(1, 7)
 		.emit_strings = 1,
-#endif
 	};
 	struct btf_dump *d;
 	size_t btf_size;

tools/perf/util/bpf-utils.h

···
        (LIBBPF_MAJOR_VERSION > (major) ||                              \
         (LIBBPF_MAJOR_VERSION == (major) && LIBBPF_MINOR_VERSION >= (minor)))
 
+#if LIBBPF_CURRENT_VERSION_GEQ(1, 7)
+// libbpf 1.7+ support the btf_dump_type_data_opts.emit_strings option.
+#define HAVE_LIBBPF_STRINGS_SUPPORT 1
+#endif
+
 /*
  * Get bpf_prog_info in continuous memory
  *