skip neon intrinsics in libpng when neon is not available

third_party/libpng/libpng.gyp

 # Copyright (c) 2012 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.
 
 {
   'targets': [
     {
       'target_name': 'libpng',
       'dependencies': [
         '../zlib/zlib.gyp:zlib',
@@ skipping 52 matching lines @@
           'defines': [
             'PNG_INTEL_SSE_OPT=1',
           ],
           'sources': [
             'contrib/intel/intel_init.c',
             'contrib/intel/filter_sse2_intrinsics.c',
           ],
         }],
 
         # ARM optimizations
-        [ '(target_arch=="arm" or target_arch=="arm64") and OS!="ios"', {
+        [ '(target_arch=="arm" or target_arch=="arm64") and OS!="ios" and arm_neon==1', {
           'defines': [
             'PNG_ARM_NEON_OPT=2',
             'PNG_ARM_NEON_IMPLEMENTATION=1',
           ],
           'sources': [
             'arm/arm_init.c',
             'arm/filter_neon_intrinsics.c',
           ],
         }],
       
@@ skipping 16 matching lines @@
             ],
           },
         }],
         ['OS=="android"', {
           'toolsets': ['target', 'host'],
         }],
       ],
     },
   ]
 }