Add support for Fuchsia

src/ports/SkOSFile_stdio.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkOSFile.h"
 #include "SkTypes.h"
 
 #include <errno.h>
 #include <stdio.h>
 #include <sys/stat.h>
 
+#ifdef SK_BUILD_FOR_UNIX
+#include <unistd.h>
+#endif
+
 #ifdef _WIN32
 #include <direct.h>
 #include <io.h>
 #endif
 
 #ifdef SK_BUILD_FOR_IOS
 #import <CoreFoundation/CoreFoundation.h>
 
 static FILE* ios_open_from_bundle(const char path[], const char* perm) {
     // Get a reference to the main bundle
@@ skipping 174 matching lines @@
 #else
     retval = mkdir(path, 0777);
 #endif
     if (0 == retval) {
         return true;
     } else {
         fprintf(stderr, "sk_mkdir: error %d creating dir '%s'\n", errno, path);
         return false;
     }
 }