[gn build] Port 8cbe371

Author: llvmgnsyncbot

llvm/utils/gn/secondary/llvm/unittests/ADT/BUILD.gn

@@ -80,6 +80,7 @@ unittest("ADTTests") {
     "TinyPtrVectorTest.cpp",
     "TripleTest.cpp",
     "TwineTest.cpp",
+    "TypeTraitsTest.cpp",
     "WaymarkingTest.cpp",
   ]
 }