Use strongly typed mu.Stacks, not strings, for CloudFormation's dependsOn

lib/aws/cloudformation/resource.ts

@@ -17,6 +17,6 @@ export interface ResourceArgs {
     // An optional list of properties to map.
     readonly properties?: any /*actually, JSON-like*/;
     // An optional list of other CloudFormation resources that this depends on.
-    readonly dependsOn?: string[];
+    readonly dependsOn?: mu.Stack[];
 }
 

lib/aws/ec2/route.ts

@@ -14,7 +14,7 @@ export class Route extends cloudformation.Resource {
         super(ctx, {
             resource: "AWS::EC2::Route",
             dependsOn: [
-                "vpcGatewayAttachment",
+                args.vpcGatewayAttachment,
             ],
             properties: args,
         });