Revert "Merge pull request #59220 from kateinoigakukun/katei/dont-use-gettid-wrapper"

This reverts commit 58081c8, reversing
changes made to 94c9ce6.

Author: ahoppen

include/swift/Threading/Impl/Linux/ulock.h

@@ -46,7 +46,7 @@ typedef std::int32_t ulock_t;
 inline int ulock_get_tid(void) {
   static __thread int tid;
   if (tid == 0)
-    tid = syscall(SYS_gettid);
+    tid = gettid();
   return tid;
 }