threads: add a thread_local autoconf check

src/sync.cpp

@@ -11,6 +11,9 @@
 #include <stdio.h>
 
 #ifdef DEBUG_LOCKCONTENTION
+#if !defined(HAVE_THREAD_LOCAL)
+static_assert(false, "thread_local is not supported");
+#endif
 void PrintLockContention(const char* pszName, const char* pszFile, int nLine)
 {
     LogPrintf("LOCKCONTENTION: %s\n", pszName);