Fix usage of SK_BUILD_* defines.

dm/DMWriteTask.cpp

 #include "DMWriteTask.h"
 
 #include "DMUtil.h"
 #include "SkColorPriv.h"
 #include "SkCommonFlags.h"
 #include "SkData.h"
 #include "SkImageEncoder.h"
 #include "SkMD5.h"
 #include "SkMallocPixelRef.h"
 #include "SkOSFile.h"
@@ skipping 101 matching lines @@
         mode = fSuffixes.fromBack(1);
     }
 
     JsonData entry = { fBaseName, config, mode, fSourceType, md5 };
     {
         SkAutoMutexAcquire lock(&gJsonDataLock);
         gJsonData.push_back(entry);
     }
 
     SkString dir(FLAGS_writePath[0]);
-#if SK_BUILD_FOR_IOS
+#if defined(SK_BUILD_FOR_IOS)
     if (dir.equals("@")) {
         dir.set(FLAGS_resourcePath[0]);
     }
 #endif
     this->makeDirOrFail(dir);
 
     SkString path;
     if (FLAGS_nameByHash) {
         // Flat directory of hash-named files.
         path = SkOSPath::Join(dir.c_str(), md5.c_str());
@@ skipping 69 matching lines @@
         }
     }
 
     SkString path = SkOSPath::Join(FLAGS_writePath[0], "dm.json");
     SkFILEWStream stream(path.c_str());
     stream.writeText(Json::StyledWriter().write(root).c_str());
     stream.flush();
 }
 
 }  // namespace DM