Add Go build support for GN.

mojo/go/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/go/rules.gni")
+
+group("go") {

[brettw, 2014/09/16 22:58:55]

I'm not really sure what this is supposed to be.

I think I might have a mojo_use_go flag in a .gni file that you can use from
various mojo places. Then you would declare the dependencies conditionally on
that so the root mojo file wouldn't even reference this if go id disabled, and
you can also remove the condition in the test rule on having the binary be
undefined (you should assert that it's defined if you want go to run).

[tburkard, 2014/09/17 12:06:45]

This group("go") was copied from qsr's python stuff. Ben, what is the purpose of
group("python")?
Done.

[qsr, 2014/09/17 12:30:25]

 I do not think I have an empty group anywhere. Which one are you referring to?

[tburkard, 2014/09/17 13:30:46]

Fixed per discussion with qsr.

+
+}
+
+go_test_binary("system_test") {
+#  go_base_module = "mojo"
+  sources = [
+    "tests/system_test.go",

[qsr, 2014/09/18 08:30:38]

Why don't you depend on all the other .go files?

Also, how would it work in the end, can you do go libraries and depend on that
in final executable? Otherwise, will you need to repeat the dependencies on go
files?

 Or can you use source_set to define you libraries? I do not know how source_set
and templates interact.

[tburkard, 2014/09/18 14:23:42]

Yup, that's what I'm not sure, how to express these dependencies.
Dependencies on (i) the other go code
(ii) the GYP lib.

Brett, can you provide some input perhaps?

Maybe easier to set up some time to chat, what do you think?

Thanks.

+  ]
+#  deps = [
+#    "//mojo/system",
+#  ]
+#  datadeps = [
+#    "//mojo/public/python:system",
+#  ]
+}