Fix iOS build.

src/images/SkForceLinking.cpp

Index: src/images/SkForceLinking.cpp
diff --git a/src/images/SkForceLinking.cpp b/src/images/SkForceLinking.cpp
index c8ea1f98e621aa8315ec96fe6625449c6dbfb428..e4dc60a4480b76e7a7ce3f6bddc16ce98b850e51 100644
--- a/src/images/SkForceLinking.cpp
+++ b/src/images/SkForceLinking.cpp
@@ -20,10 +20,11 @@ int SkForceLinking(bool doNotPassTrue) {
         CreateICOImageDecoder();
         CreateWBMPImageDecoder();
         // Only link GIF and PNG on platforms that build them. See images.gyp
-#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN) && !defined(SK_BUILD_FOR_NACL)
+#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN) && !defined(SK_BUILD_FOR_NACL) \
+        && !defined(SK_BUILD_FOR_IOS)
         CreateGIFImageDecoder();
 #endif
-#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN)
+#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN) && !defined(SK_BUILD_FOR_IOS)
         CreatePNGImageDecoder();
 #endif
         return -1;