Try to fix thread name truncation on non-Windows.

llvm-svn: 296976
diff --git a/llvm/lib/Support/Threading.cpp b/llvm/lib/Support/Threading.cpp
index e49d328..6a10b98 100644
--- a/llvm/lib/Support/Threading.cpp
+++ b/llvm/lib/Support/Threading.cpp
@@ -49,6 +49,8 @@
 
 uint64_t llvm::get_threadid() { return 0; }
 
+uint32_t llvm::get_max_thread_name_length() { return 0; }
+
 void llvm::set_thread_name(const Twine &Name) {}
 
 void llvm::get_thread_name(SmallVectorImpl<char> &Name) { Name.clear(); }