[gn build] Port 160f5ca

Author: llvmgnsyncbot

llvm/utils/gn/secondary/llvm/lib/Target/AVR/BUILD.gn

@@ -49,6 +49,7 @@ static_library("LLVMAVRCodeGen") {
     "AVRSubtarget.cpp",
     "AVRTargetMachine.cpp",
     "AVRTargetObjectFile.cpp",
+    "AVRTargetTransformInfo.cpp",
   ]
 }