Only pass android_toolchain in android builds.

dl/dl.gyp

 #  Copyright (c) 2013 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.
 
 {
   'variables' : {
     # Override this value to build with small float FFT tables
     'big_float_fft%' : 1,
     'use_lto%': 0,
   },
   'target_defaults': {
     'include_dirs': [
       '../',
     ],
     'conditions' : [
       ['target_arch=="arm"', {
         'conditions' : [
           ['clang==1', {
             # TODO(hans) Enable integrated-as (crbug.com/124610).
-            'cflags': [
-              '-fno-integrated-as',
-              '-B<(android_toolchain)',  # Else /usr/bin/as gets picked up.
+            'cflags': [ '-fno-integrated-as' ],
+            'conditions': [
+              ['OS == "android"', {
+                # Else /usr/bin/as gets picked up.
+                'cflags': [ '-B<(android_toolchain)' ],
+              }],
             ],
           }],
           ['arm_neon==1', {
             # Enable build-time NEON selection.
             'defines': ['DL_ARM_NEON',],
             'direct_dependent_settings': {
               'defines': ['DL_ARM_NEON',],
             },
           }],
           ['arm_neon==0 and arm_neon_optional==1', {
@@ skipping 264 matching lines @@
                 '-flto',
                 '-ffat-lto-objects',
               ],
             }],
           ],
         },
       ],
     }],
   ],
 }