[Tsan] Fix test.h to work on FreeBSD

[dvyukov]

LGTM with nits

test/tsan/test.h

15

2 spaces instead of 4

17

2 spaces instead of 4

test/tsan/test.h

 #include <pthread.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <dlfcn.h>
 #include <stddef.h>
 
 // TSan-invisible barrier.
 // Tests use it to establish necessary execution order in a way that does not
 // interfere with tsan (does not establish synchronization between threads).
 __typeof(pthread_barrier_wait) *barrier_wait;
 
 void barrier_init(pthread_barrier_t *barrier, unsigned count) {
+#if defined(__FreeBSD__)
+    static const char libpthread_name[] = "libpthread.so";
+#else
+    static const char libpthread_name[] = "libpthread.so.0";
+#endif
+
   if (barrier_wait == 0) {
-    void *h = dlopen("libpthread.so.0", RTLD_LAZY);
+    void *h = dlopen(libpthread_name, RTLD_LAZY);
     if (h == 0) {
-      fprintf(stderr, "failed to dlopen libpthread.so.0, exiting\n");
+      fprintf(stderr, "failed to dlopen %s, exiting\n", libpthread_name);
       exit(1);
     }
     barrier_wait = (__typeof(barrier_wait))dlsym(h, "pthread_barrier_wait");
     if (barrier_wait == 0) {
       fprintf(stderr, "failed to resolve pthread_barrier_wait, exiting\n");
       exit(1);
     }
   }