Update version of Go to 1.5

mojo/go/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.
 
 declare_args() {
   # By default, there is no go build tool, because go builds are not supported.
   go_build_tool = ""
 }
 
 # Declare a go library.
@@ skipping 119 matching lines @@
     args += [
       "--",
       "${go_build_tool}",
       rebase_path(build_dir, root_build_dir),
       rebase_path(target_out_dir, root_build_dir) + "/${target_name}",
       rebase_path("//", root_build_dir),
       rebase_path(root_out_dir, root_build_dir),
       "-I" + rebase_path("//"),
       "-L" + rebase_path(target_out_dir) + " -l" + static_library_name + "",
       "build",
-      "-ldflags=-shared",
     ]
-    if (is_linux) {
-      args += [ "-buildmode=c-shared" ]
-    }
+    args += [ "-buildmode=c-shared" ]
     args += rebase_path(invoker.sources, build_dir)
   }
 
   copy(target_name) {
     deps = [
       ":${go_library_name}",
     ]
     sources = [
       "${target_out_dir}/${go_library_name}",
     ]
     outputs = [
       "${root_out_dir}/${target_name}.mojo",
     ]
   }
 }