Don't #include internal header <os/tsd.h> on platforms that don't need it.

Swift SVN r8468

stdlib/runtime/Alloc.cpp

@@ -17,8 +17,6 @@
 #include "swift/Runtime/Alloc.h"
 #include "swift/Runtime/Metadata.h"
 #include "llvm/Support/MathExtras.h"
-// We'll include this and do per-thread clean up once we actually have threads
-//#include <System/pthread_machdep.h>
 #include "Private.h"
 #include <cassert>
 #include <cstring>
@@ -373,6 +371,11 @@ void *swift::swift_slowAlloc(size_t bytes, uint64_t flags) {
 // These are implemented in FastEntryPoints.s on some platforms.
 #ifndef SWIFT_HAVE_FAST_ENTRY_POINTS
 
+#if __has_include(<os/tsd.h>)
+// OS X and iOS internal version
+
+#include <os/tsd.h>
+
 struct AllocCacheEntry {
   struct AllocCacheEntry *next;
 };
@@ -451,6 +454,12 @@ void swift::swift_rawDealloc(void *ptr, AllocIndex idx) {
   setRawAllocCacheEntry(idx, cur);
 }
 
+#else
+
+# error no thread-local cache implementation for this platform
+
+#endif
+
 // !SWIFT_HAVE_FAST_ENTRY_POINTS
 #endif