[sanitizers] using execv instead of execve with null env.

[aizatsky]

Summary

We used to call execv anyway.

lib/sanitizer_common/sanitizer_posix_libcdep.cc

if (pid == 0) {
     if (stderr_fd != kInvalidFd) {
       internal_close(STDERR_FILENO);
       internal_dup2(stderr_fd, STDERR_FILENO);
       internal_close(stderr_fd);
     }
 
     for (int fd = sysconf(_SC_OPEN_MAX); fd > 2; fd--) internal_close(fd);
 
-    internal_execve(program, const_cast<char **>(&argv[0]), nullptr);
+    execv(program, const_cast<char **>(&argv[0]));
     internal__exit(1);
   }
 
   return pid;
 }
 
 bool IsProcessRunning(pid_t pid) {
   int process_status;