[gn build] Port 287b944

Author: llvmgnsyncbot

llvm/utils/gn/secondary/lldb/source/Plugins/Language/CPlusPlus/BUILD.gn

@@ -65,6 +65,7 @@ static_library("CPlusPlus") {
     "MsvcStlAtomic.cpp",
     "MsvcStlSmartPointer.cpp",
     "MsvcStlTuple.cpp",
+    "MsvcStlUnordered.cpp",
     "MsvcStlVariant.cpp",
     "MsvcStlVector.cpp",
   ]