Enable cross compile to android from mac.

build/config/android/rules.gni

 # 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("//base/android/linker/config.gni")
 import("//build/config/android/config.gni")
 import("//build/config/android/internal_rules.gni")
 import("//tools/grit/grit_rule.gni")
 import("//tools/relocation_packer/config.gni")
 
@@ skipping 1554 matching lines @@
     }
     deps = [
       "//base:base_java",
       "//build/android/pylib/remote/device/dummy:remote_device_dummy_apk",
       "//testing/android/appurify_support:appurify_support_java",
     ]
     if (defined(invoker.deps)) {
       deps += invoker.deps
     }
     datadeps = [
-      "//tools/android/forwarder2",
       "//tools/android/md5sum",
     ]
+    if (host_os == "linux") {
+      datadeps += [ "//tools/android/forwarder2" ]
+    }
     if (defined(invoker.datadeps)) {
       datadeps += invoker.datadeps
     }
   }
 }
 
 # Generate .java files from .aidl files.
 #
 # This target will store the .java files in a srcjar and should be included in
 # an android_library or android_apk's srcjar_deps.
@@ skipping 215 matching lines @@
 template("uiautomator_test") {
   set_sources_assignment_filter([])
   if (defined(invoker.testonly)) {
     testonly = invoker.testonly
   }
   assert(target_name != "")
   assert(invoker.deps != [] || true)
   group(target_name) {
   }
 }