gn: fix fiddle

tools/fiddle/fiddle_main.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <stdio.h>
 #include <stdlib.h>
+#include "SkForceLinking.h"
+
+__SK_FORCE_IMAGE_DECODER_LINKING;
 
 #include "fiddle_main.h"
 
 // Globals externed in fiddle_main.h
 SkBitmap source;
 sk_sp<SkImage> image;
 
 static void encode_to_base64(const void* data, size_t size, FILE* out) {
     const uint8_t* input = reinterpret_cast<const uint8_t*>(data);
     const uint8_t* end = &input[size];
@@ skipping 132 matching lines @@
 
     printf("{\n");
     dump_output(rasterData, "Raster", !gpuData && !pdfData && !skpData);
     dump_output(gpuData, "Gpu", !pdfData && !skpData);
     dump_output(pdfData, "Pdf", !skpData);
     dump_output(skpData, "Skp");
     printf("}\n");
 
     return 0;
 }