Add Go build support for GN.

build/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 test binary target.
+#
+# The target generates a go test executable, linking against other C code,
+# which is compiled into a static library and linked against Go.
+#
+# Only works on linux. |go_build_tool| must be set to the absolute path
+# of the go build tool.
+#
+# Variables (all required)
+#   sources: list of .go files to compile
+#   static_library_sources: list of C sources needed for the static library
+#   deps: dependencies for the static library
+
+template("go_test_binary") {
+  # Only available on linux for now.
+  assert(is_linux)
+  assert(defined(invoker.sources))
+  assert(go_build_tool != "")
+
+  static_library_name = target_name + "_static_library"
+
+  static_library(static_library_name) {
+    sources = invoker.static_library_sources

[qsr, 2014/09/26 13:33:41]

I do not think you should force C sources. When the core API will be done, the
rest should be pure go.  You should check if the variable exists. You need to
check defined(invoker.static_library_sources)

[brettw, 2014/09/26 18:15:34]

The problem is you can't make a static library if there are no sources. If you
want to support "no C sources" you either need to use a source set (which would
then not be linkable with your script), or have a mode where it doesn't produce
a static library and you presumably don't lass the "-l" to the script.

+    deps = invoker.deps
+    complete_static_lib = true
+  }
+
+  action(target_name) {
+    deps = [
+      ":$static_library_name",
+    ]
+    script = "//build/go/go.py"
+    outputs = [ "${target_out_dir}/${target_name}" ]
+    # Since go test does not permit specifying an output directory or output
+    # binary name, we create a temporary build directory, and the python
+    # script will later identify the output, copy it to the target location,
+    # and clean up the temporary build directory.
+    build_dir = "${target_out_dir}/${target_name}_build"
+    args = [
+      "--", 
+      "${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),
+      "-I" + rebase_path("//"),
+      " -L" + rebase_path(target_out_dir) +
+      " -L" + rebase_path(root_build_dir + "/obj/third_party/libevent") +
+      " -l" + static_library_name +
+      " -lstdc++ -lpthread -lm -lglib-2.0 -levent",
+      "test", "-c",
+    ] + rebase_path(invoker.sources, build_dir)
+  }
+}