diff --git a/llvm/lib/ToolDrivers/llvm-lib/Options.td b/llvm/lib/ToolDrivers/llvm-lib/Options.td
--- a/llvm/lib/ToolDrivers/llvm-lib/Options.td
+++ b/llvm/lib/ToolDrivers/llvm-lib/Options.td
@@ -43,4 +43,5 @@
 // The flags below do nothing. They are defined only for lib.exe compatibility.
 //==============================================================================
 
+def ltcg : F<"ltcg">;
 def nologo : F<"nologo">;