Set rtc_prefer_fixed_point to true on arm64 to match GYP

webrtc/build/webrtc.gni

 # Copyright (c) 2014 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.
 
 import("//build/config/arm.gni")
 import("//build/config/features.gni")
@@ skipping 53 matching lines @@
   } else {
     rtc_include_tests = true
     rtc_restrict_logging = false
   }
 
   if (is_ios) {
     rtc_build_libjpeg = false
     rtc_enable_protobuf = false
   }
 
-  if (current_cpu == "arm") {
+  if (current_cpu == "arm" || current_cpu == "arm64") {
     rtc_prefer_fixed_point = true
   }
 
   # TODO(ljubomir): Unset rtc_use_openmax_dl for mips64el once mips64el gets
   # supported in GN (since openmax_dl is not supported for mips64el).
   if (!is_ios && (current_cpu != "arm" || arm_version >= 7)) {
     rtc_use_openmax_dl = true
   } else {
     rtc_use_openmax_dl = false
   }
@@ skipping 31 matching lines @@
 declare_args() {
   # Include the iLBC audio codec?
   rtc_include_ilbc = !(build_with_chromium || build_with_mozilla)
 }
 
 # Make it possible to provide custom locations for some libraries (move these
 # up into declare_args should we need to actually use them for the GN build).
 rtc_libvpx_dir = "//third_party/libvpx_new"
 rtc_libyuv_dir = "//third_party/libyuv"
 rtc_opus_dir = "//third_party/opus"