[TSan][Darwin] Enable test on non-macOS platforms

After removing the unnecessary `-mmacosx-version-min=10.12` compiler
flag this test can run on all platforms.  I confirmed that this test is
green for iOS, iOS simulator, and watchOS simulator.

Differential Revision: https://reviews.llvm.org/D85952

compiler-rt/test/tsan/Darwin/os_unfair_lock.c

@@ -1,8 +1,6 @@
-// RUN: %clang_tsan %s -o %t -mmacosx-version-min=10.12
+// RUN: %clang_tsan %s -o %t
 // RUN: %run %t 2>&1 | FileCheck %s --implicit-check-not='ThreadSanitizer'
 
-// UNSUPPORTED: ios
-
 #include <os/lock.h>
 #include <pthread.h>
 #include <stdio.h>