[gn build] Port f4e2d7b

Author: llvmgnsyncbot

llvm/utils/gn/secondary/llvm/lib/Transforms/Coroutines/BUILD.gn

@@ -18,6 +18,7 @@ static_library("Coroutines") {
     "CoroFrame.cpp",
     "CoroSplit.cpp",
     "Coroutines.cpp",
+    "SpillUtils.cpp",
     "SuspendCrossingInfo.cpp",
   ]
 }