Revert "[iOS] Defaults to use system libjpeg on iOS."

build/secondary/third_party/libjpeg_turbo/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Do not use the targets in this file unless you need a certain libjpeg
 # implementation. Use the meta target //third_party:jpeg instead.
 
 import("//build/config/sanitizers/sanitizers.gni")
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
@@ skipping 64 matching lines @@
     }
 
     if (is_win) {
       defines += [ "MSVC" ]
       include_dirs = [ "win" ]
       if (current_cpu == "x86") {
         defines += [ "WIN32" ]
       } else {
         defines += [ "WIN64" ]
       }
-    } else if (is_mac) {
+    } else if (is_mac || is_ios) {
       defines += [ "MACHO" ]
       include_dirs = [ "mac" ]
     } else if (is_linux || is_android) {
       defines += [ "ELF" ]
       include_dirs = [ "linux" ]
     }
   }
 }
 
 source_set("simd") {
@@ skipping 109 matching lines @@
   # MemorySanitizer doesn't support assembly code, so keep it disabled in
   # MSan builds for now.
   if (is_msan) {
     sources += [ "jsimd_none.c" ]
   } else {
     deps = [
       ":simd",
     ]
   }
 }