Fix compilation without pthreads.

Patch by Xerxes Ranby.

llvm-svn: 74283

llvm/lib/System/Unix/ThreadLocal.inc

@@ -20,6 +20,6 @@ namespace llvm {
 using namespace sys;
 ThreadLocalImpl::ThreadLocalImpl() { }
 ThreadLocalImpl::~ThreadLocalImpl() { }
-void ThreadLocalImpl::setInstance(void* d) { data = d; }
-void* ThreadLocalImpl::getInstance() { return data; }
-}
+void ThreadLocalImpl::setInstance(const void* d) { data = const_cast<void*>(d);}
+const void* ThreadLocalImpl::getInstance() { return data; }
+}