Allow ci_runner to install kythe (#6479)

enterprise/server/cmd/ci_runner/main.go

@@ -97,6 +97,11 @@ const (
 	repoUserEnvVarName         = "REPO_USER"
 	repoTokenEnvVarName        = "REPO_TOKEN"
 
+	// Only set if --install_kythe is true.
+	kytheDirEnvVarName = "KYTHE_DIR"
+	kytheDirName       = "kythe-v0.0.67"
+	kytheArchiveURL    = "https://storage.googleapis.com/buildbuddy-tools/archives/kythe-v0.0.67.tar.gz"
+
 	// Exit code placeholder used when a command doesn't return an exit code on its own.
 	noExitCode         = -1
 	failedExitCodeName = "Failed"
@@ -160,6 +165,7 @@ var (
 	bazelStartupFlags = flag.String("bazel_startup_flags", "", "Startup flags to pass to bazel. The value can include spaces and will be properly tokenized.")
 	extraBazelArgs    = flag.String("extra_bazel_args", "", "Extra flags to pass to the bazel command. The value can include spaces and will be properly tokenized.")
 	debug             = flag.Bool("debug", false, "Print additional debug information in the action logs.")
+	installKythe      = flag.Bool("install_kythe", false, "If true, install kythe in the workspace root and set the KYTHE_DIR env var to the installed location")
 
 	// Test-only flags
 	fallbackToCleanCheckout = flag.Bool("fallback_to_clean_checkout", true, "Fallback to cloning the repo from scratch if sync fails (for testing purposes only).")
@@ -244,6 +250,25 @@ func provisionArtifactsDir(ws *workspace, bazelCommandIndex int) error {
 	return nil
 }
 
+func provisionKythe(ctx context.Context, ws *workspace) error {
+	kytheRootPath := filepath.Join(ws.rootDir, kytheDirName)
+	if _, err := os.Stat(kytheRootPath); err == nil {
+		return nil // dir already exists; we're done.
+	}
+	if err := os.MkdirAll(kytheRootPath, 0755); err != nil {
+		return err
+	}
+	cmd := fmt.Sprintf(`curl -sL "%s" | tar -xz -C %s --strip-components 1`, kytheArchiveURL, kytheRootPath)
+	args := []string{"-c", cmd}
+	if err := runCommand(ctx, "bash", args, nil /*=env*/, "" /*=dir*/, ws.log); err != nil {
+		return err
+	}
+	if err := os.Setenv(kytheDirEnvVarName, kytheRootPath); err != nil {
+		return err
+	}
+	return nil
+}
+
 type buildEventReporter struct {
 	isWorkflow bool
 	apiKey     string
@@ -922,6 +947,12 @@ func (ar *actionRunner) Run(ctx context.Context, ws *workspace) error {
 		}
 	}()
 
+	if *installKythe {
+		if err := provisionKythe(ctx, ws); err != nil {
+			return err
+		}
+	}
+
 	for i, bazelCmd := range action.BazelCommands {
 		cmdStartTime := time.Now()