[gn build] Port 136c8f5

Author: llvmgnsyncbot

llvm/utils/gn/secondary/llvm/tools/llvm-reduce/BUILD.gn

@@ -14,6 +14,7 @@ executable("llvm-reduce") {
     "deltas/ReduceArguments.cpp",
     "deltas/ReduceAttributes.cpp",
     "deltas/ReduceBasicBlocks.cpp",
+    "deltas/ReduceFunctionBodies.cpp",
     "deltas/ReduceFunctions.cpp",
     "deltas/ReduceGlobalVars.cpp",
     "deltas/ReduceInstructions.cpp",