[MIPS64] Start using Clang IAS for mips64 Android

build/config/android/BUILD.gn

 # Copyright 2014 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/sanitizers/sanitizers.gni")
 
 assert(is_android)
 
 # This is included by reference in the //build/config/compiler config that
 # is applied to all targets. It is here to separate out the logic that is
 # Android-only.
 config("compiler") {
   cflags = [
     "-ffunction-sections",
     "-fno-short-enums",
   ]
   defines = [
     "ANDROID",
 
     # The NDK has these things, but doesn't define the constants to say that it
     # does. Define them here instead.
     "HAVE_SYS_UIO_H",
 
     # Forces full rebuilds on NDK rolls.
     "ANDROID_NDK_VERSION=${android_ndk_version}",
   ]
 
   if (is_clang) {
-    rebased_android_toolchain_root =
-        rebase_path(android_toolchain_root, root_build_dir)
-    assert(rebased_android_toolchain_root != "")  # Mark as used.
     if (current_cpu == "mips64el") {
       cflags += [
-        # TODO(gordanac) Enable integrated-as.
-        "-fno-integrated-as",
-        "-B${rebased_android_toolchain_root}/bin",  # Else /usr/bin/as gets picked up.
+        # Have to force IAS for mips64.
+        "-fintegrated-as",
       ]
     }
   } else {
     # Clang doesn't support these flags.
     cflags += [ "-finline-limit=64" ]
   }
 
   ldflags = [
     "-Wl,--build-id=sha1",
     "-Wl,--no-undefined",
@@ skipping 185 matching lines @@
 
       # Avoid errors with current NDK:
       # "third_party/android_tools/ndk/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.6/include/arm_neon.h:3426:3: error: argument must be a constant"
       "-finstrument-functions-exclude-file-list=arm_neon.h",
     ]
   }
 }
 
 config("no_cygprofile_instrumentation") {
 }