Default to building instead of just linking libpng for Android

third_party/libpng/libpng.gyp

 # Copyright (c) 2011 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.
 
 {
   'variables': {
     'conditions': [
-      [ 'os_posix == 1 and OS != "mac"', {
+      [ 'os_posix == 1 and OS != "mac" and OS != "android"', {
         # Link to system .so since we already use it due to GTK.
         'use_system_libpng%': 1,
       }, {  # os_posix != 1 or OS == "mac"
         'use_system_libpng%': 0,
       }],
     ],
   },
   'conditions': [
     ['use_system_libpng==0', {
       'targets': [
@@ skipping 93 matching lines @@
             ],
             'libraries': [
               '<!@(<(pkg-config) --libs-only-l libpng)',
             ],
           },
         },
       ],
     }],
   ],
 }