Implement the 'shared' subcommand for mmutex

mmutex/cmd/mmutex/test_helpers.go

Index: mmutex/cmd/mmutex/test_helpers.go
diff --git a/mmutex/cmd/mmutex/test_helpers.go b/mmutex/cmd/mmutex/test_helpers.go
new file mode 100644
index 0000000000000000000000000000000000000000..5a1814c6b1deb690c7bb04ad88acf049e0703a9d
--- /dev/null
+++ b/mmutex/cmd/mmutex/test_helpers.go
@@ -0,0 +1,27 @@
+// Copyright 2017 The LUCI Authors.
+//
+// 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 main
+
+import (
+	"runtime"
+)
+
+func createCommand(command []string) []string {
+	if runtime.GOOS == "windows" {
+		return append([]string{"cmd", "/c"}, command...)
+	}
+
+	return command
+}