goma_ctl.py ensure_start in Soong UI.

As suggested in b/118390303#comment18, let me run
"goma_ctl.py ensure_start" in soong UI.

Bug: 118390303
Test: stop compiler_proxy, and execute following command:
Test: USE_GOMA=true lunch aosp_arm-eng
Test: and confirms compiler_proxy is running.
Change-Id: I859daae6ae2399c5b6bce2fafd874dfdb7c6aae0
Signed-off-by: Yoshisato Yanagisawa <yyanagisawa@google.com>

ui/build/Android.bp

@@ -47,6 +47,7 @@ bootstrap_go_package {
         "environment.go",
         "exec.go",
         "finder.go",
+        "goma.go",
         "kati.go",
         "ninja.go",
         "path.go",

ui/build/build.go

@@ -156,6 +156,11 @@ func Build(ctx Context, config Config, what int) {
 
 	SetupPath(ctx, config)
 
+	if config.StartGoma() {
+		// Ensure start Goma compiler_proxy
+		startGoma(ctx, config)
+	}
+
 	if what&BuildProductConfig != 0 {
 		// Run make for product config
 		runMakeProductConfig(ctx, config)

ui/build/config.go

@@ -478,6 +478,20 @@ func (c *configImpl) UseGoma() bool {
 	return false
 }
 
+func (c *configImpl) StartGoma() bool {
+	if !c.UseGoma() {
+		return false
+	}
+
+	if v, ok := c.environ.Get("NOSTART_GOMA"); ok {
+		v = strings.TrimSpace(v)
+		if v != "" && v != "false" {
+			return false
+		}
+	}
+	return true
+}
+
 // RemoteParallel controls how many remote jobs (i.e., commands which contain
 // gomacc) are run in parallel.  Note the parallelism of all other jobs is
 // still limited by Parallel()

ui/build/goma.go

@@ -0,0 +1,48 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build
+
+import (
+	"errors"
+	"path/filepath"
+
+	"android/soong/ui/metrics"
+)
+
+const gomaCtlScript = "goma_ctl.py"
+
+var gomaCtlNotFound = errors.New("goma_ctl.py not found")
+
+func startGoma(ctx Context, config Config) error {
+	ctx.BeginTrace(metrics.RunSetupTool, "goma_ctl")
+	defer ctx.EndTrace()
+
+	var gomaCtl string
+	if gomaDir, ok := config.Environment().Get("GOMA_DIR"); ok {
+		gomaCtl = filepath.Join(gomaDir, gomaCtlScript)
+	} else if home, ok := config.Environment().Get("HOME"); ok {
+		gomaCtl = filepath.Join(home, "goma", gomaCtlScript)
+	} else {
+		return gomaCtlNotFound
+	}
+
+	cmd := Command(ctx, config, "goma_ctl.py ensure_start", gomaCtl, "ensure_start")
+
+	if err := cmd.Run(); err != nil {
+		ctx.Fatalf("goma_ctl.py ensure_start failed with: %v", err)
+	}
+
+	return nil
+}