Add a [rtc_]build_with_neon variable to unify conditions.

webrtc/build/common.gypi

 # Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 # This file contains common settings for building WebRTC components.
 
@@ skipping 103 matching lines @@
     # Link-Time Optimizations
     # Executes code generation at link-time instead of compile-time
     # https://gcc.gnu.org/wiki/LinkTimeOptimization
     'use_lto%': 0,
 
     # Defer ssl perference to that specified through sslconfig.h instead of
     # choosing openssl or nss directly.  In practice, this can be used to
     # enable schannel on windows.
     'use_legacy_ssl_defaults%': 0,
 
+    # Determines whether NEON code will be built. It might not be selected at
+    # run-time.
+    'build_with_neon%': 0,
+
     'conditions': [
       ['build_with_chromium==1', {
         # Exclude pulse audio on Chromium since its prerequisites don't require
         # pulse audio.
         'include_pulse_audio%': 0,
 
         # Exclude internal ADM since Chromium uses its own IO handling.
         'include_internal_audio_device%': 0,
       }, {  # Settings for the standalone (not-in-Chromium) build.
         # TODO(andrew): For now, disable the Chrome plugins, which causes a
@@ skipping 121 matching lines @@
               '-Wthread-safety',
             ],
           }],
         ],
       }],
       ['target_arch=="arm64"', {
         'defines': [
           'WEBRTC_ARCH_ARM64',
           'WEBRTC_HAS_NEON',
         ],
+        'variables': {'build_with_neon%': 1,},
       }],
       ['target_arch=="arm"', {
         'defines': [
           'WEBRTC_ARCH_ARM',
         ],
         'conditions': [
           ['arm_version>=7', {
             'defines': ['WEBRTC_ARCH_ARM_V7',],
             'conditions': [
               ['arm_neon==1', {
                 'defines': ['WEBRTC_HAS_NEON',],
+                'variables': {'build_with_neon%': 1,},
               }],
               ['arm_neon==0 and arm_neon_optional==1', {
                 'defines': ['WEBRTC_DETECT_NEON',],
+                'variables': {'build_with_neon%': 1,},
               }],
             ],
           }],
         ],
       }],
       ['target_arch=="mipsel" and mips_arch_variant!="r6"', {
         'defines': [
           'MIPS32_LE',
         ],
         'conditions': [
@@ skipping 142 matching lines @@
           # of a more specific macro.
           'defines': [
             'WEBRTC_POSIX',
           ],
         }],
       ],
     },
   }, # target_defaults
 }