Fix gitignore and add prepare.go

.gitignore

@@ -6,7 +6,6 @@ singularity-*.tar.gz
 *.m4
 *.pyc
 *.swp
-singularity
 generate_docs
 
 .vscode

src/runtime/engines/singularity/prepare.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2018, Sylabs Inc. All rights reserved.
+// This software is licensed under a 3-clause BSD license. Please consult the
+// LICENSE file distributed with the sources of this project regarding your
+// rights to use or distribute this software.
+
+package singularity
+
+import (
+	"fmt"
+)
+
+// PrepareConfig checks and prepares the runtime engine config
+func (engine *EngineOperations) PrepareConfig() error {
+	if engine.CommonConfig.EngineName != Name {
+		return fmt.Errorf("incorrect engine")
+	}
+
+	engine.CommonConfig.OciConfig.SetProcessNoNewPrivileges(true)
+	return nil
+}