GYP changes for arm64 linux build

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 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.
 
 import("//build/config/android/config.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/toolchain.gni")
@@ skipping 515 matching lines @@
           cflags += [ "-mthumb" ]
           if (is_android && !is_clang) {
             # Clang doesn't support this option.
             cflags += [ "-mthumb-interwork" ]
           }
         }
       }
       if (arm_tune != "") {
         cflags += [ "-mtune=$arm_tune" ]
       }
+    } else if (current_cpu == "arm64") {
+      if (is_clang && !is_android && !is_nacl) {
+        cflags += [ "--target=aarch64-linux-gnu" ]
+        ldflags += [ "--target=aarch64-linux-gnu" ]
+      }
     } else if (current_cpu == "mipsel") {
       if (is_clang) {
         # Temporarily needed due to unsupported MIPS macro instructions
         # in inline asm code in third_party projects (libwebp and webrtc).
         # TODO(lmilko) Enable integrated-as.
         cflags += [ "-fno-integrated-as" ]
       }
       if (mips_arch_variant == "r6") {
         if (is_clang) {
           cflags += [
@@ skipping 918 matching lines @@
 
 if (is_ios || is_mac) {
   # On Mac and iOS, this enables support for ARC (automatic ref-counting).
   # See http://clang.llvm.org/docs/AutomaticReferenceCounting.html.
   config("enable_arc") {
     common_flags = [ "-fobjc-arc" ]
     cflags_objc = common_flags
     cflags_objcc = common_flags
   }
 }