On FreeBSD, skip the first entry in the dl_iterate_phdr list.

[dim]

Summary

Similar to NetBSD, in FreeBSD, the first returned entry when callbacks
are done via dl_iterate_phdr will return the main program. Ignore that
entry when checking that the dynamic ASan lib is loaded first.

lib/asan/asan_linux.cc

static int FindFirstDSOCallback(struct dl_phdr_info *info, size_t size,
   // Continue until the first dynamic library is found
   if (!info->dlpi_name || info->dlpi_name[0] == 0)
     return 0;
 
   // Ignore vDSO
   if (internal_strncmp(info->dlpi_name, "linux-", sizeof("linux-") - 1) == 0)
     return 0;
 
-#if SANITIZER_NETBSD
+#if SANITIZER_FREEBSD || SANITIZER_NETBSD
   // Ignore first entry (the main program)
   char **p = (char **)data;
   if (!(*p)) {
     *p = (char *)-1;
     return 0;
   }
 #endif