message: Restrict mutex static initializer test to Linux
  On macOS, libc does not have a static initializer for recursive mutexes
diff: @@ -10,10 +10,13 @@ fn main() {
  {
  test_mutex_libc_init_recursive();
  test_mutex_libc_init_normal();
  - test_mutex_libc_static_initializer_recursive();
  test_rwlock_stdlib();
  test_rwlock_libc_static_initializer();
  }
  + #[cfg(target_os = "linux")]
  + {
  + test_mutex_libc_static_initializer_recursive();
  + }
  }
  fn test_mutex_stdlib() {
  @@ -64,7 +67,7 @@ fn test_mutex_libc_init_normal() {
  }
  }
  -#[cfg(not(target_os = "windows"))]
  +#[cfg(target_os = "linux")]
  fn test_mutex_libc_static_initializer_recursive() {
  let mutex = std::cell::UnsafeCell::new(libc::PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP);
  unsafe {
  