add some basic stubs for ro volume support

engine/compiler/compiler.go

@@ -371,6 +371,11 @@ func (c *Compiler) Compile(ctx context.Context, args runtime.CompilerArgs) runti
 				ID:   id,
 				Name: id,
 				Path: k,
+
+				// TODO(bradrydzewski) the volume map does not include
+				// a read only flag and needs to be modified to provide
+				// this option.
+				ReadOnly: false,
 			},
 		}
 		spec.Volumes = append(spec.Volumes, volume)

engine/convert.go

@@ -220,6 +220,7 @@ func toMount(source *Volume, target *VolumeMount) mount.Mount {
 	}
 	if isBindMount(source) || isNamedPipe(source) {
 		to.Source = source.HostPath.Path
+		to.ReadOnly = source.HostPath.ReadOnly
 	}
 	if isTempfs(source) {
 		to.TmpfsOptions = &mount.TmpfsOptions{

engine/spec.go

@@ -105,6 +105,7 @@ type (
 		Name     string            `json:"name,omitempty"`
 		Path     string            `json:"path,omitempty"`
 		Labels   map[string]string `json:"labels,omitempty"`
+		ReadOnly bool              `json:"read_only,omitempty"`
 	}
 
 	// VolumeDevice describes a mapping of a raw block