message: Remove our implementation of pthread_spin_trylock
diff: #ifdef INSIDE_ENCLAVE
  # include <pthread.h>
  -// OpenEnclave, at this time, does not provide pthread_spin_trylock. There is
  -// currently a PR that will introduce said function and this should be removed
  -// when said function is in OpenEnclave.
  -// https://github.com/openenclave/openenclave/pull/3641
  -# ifndef VIRTUAL_ENCLAVE
  -static unsigned int _spin_set_locked(pthread_spinlock_t* spinlock)
  -{
  - unsigned int value = 1;
  -
  - asm volatile("lock xchg %0, %1;"
  - : "=r"(value) /* %0 */
  - : "m"(*spinlock), /* %1 */
  - "0"(value) /* also %2 */
  - : "memory");
  -
  - return value;
  -}
  -# endif
  -
  class SpinLock
  {
  private:
  @@ -47,11 +28,7 @@ public:
  bool try_lock()
  {
  -# ifdef VIRTUAL_ENCLAVE
  return pthread_spin_trylock(&sl) == 0;
  -# else
  - return (_spin_set_locked(&sl) == 0);
  -# endif
  }
  void unlock()
  