perf tools: Make usage of test_attr__* optional for perf-sys.h

For users of perf-sys.h outside perf, e.g. samples/bpf/bpf_load.c, it's
convenient not to depend on test_attr__*.

After commit 91854f9a077e ("perf tools: Move everything related to
sys_perf_event_open() to perf-sys.h"), all users of perf-sys.h will
depend on test_attr__enabled and test_attr__open.

This commit enables a user to define HAVE_ATTR_TEST to zero in order
to omit the test dependency.

Fixes: 91854f9a077e ("perf tools: Move everything related to sys_perf_event_open() to perf-sys.h")
Signed-off-by: Björn Töpel <[e-mail]>
Acked-by: Song Liu <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Link: http://lore.kernel.org/bpf/[e-mail]

tools/perf/perf-sys.h

···
 void test_attr__open(struct perf_event_attr *attr, pid_t pid, int cpu,
 		     int fd, int group_fd, unsigned long flags);
 
-#define HAVE_ATTR_TEST
+#ifndef HAVE_ATTR_TEST
+#define HAVE_ATTR_TEST 1
+#endif
 
 static inline int
 sys_perf_event_open(struct perf_event_attr *attr,
···
 	fd = syscall(__NR_perf_event_open, attr, pid, cpu,
 		     group_fd, flags);
 
-#ifdef HAVE_ATTR_TEST
+#if HAVE_ATTR_TEST
 	if (unlikely(test_attr__enabled))
 		test_attr__open(attr, pid, cpu, fd, group_fd, flags);
 #endif