assets: EKS not deployable via CDK Pipelines

Hi there!

I am trying to deploy an EKS cluster via CDK Pipelines. This breaks, because the assets for custom resources within EKS are referenced with absolute path in ...assets.json. This happens during cdk synth in the Pipelines build step. Then, in a later pipeline step, cdk-assets is not able to find the assets (because CodeBuild generate random temp dir names for each run) and therefor uploads empty zip files to S3. This breaks the deployment of the application stack (eks) with this error message in CloudFormation:

Uploaded file must be a non-empty zip (Service: AWSLambdaInternal; Status Code: 400; Error Code: InvalidParameterValueException; Request ID: 6443c97c-4806-4f82-8224-5a4e2afc48b2; Proxy: null)

Reproduction Steps

1. Create a CDK Pipeline according to the dev guide
2. add an EKS stack application stage via pipeline.addApplicationStage()
3. deploy the pipeline and wait for it to fail during application stack deployment

What did you expect to happen?

cdk synth should create references with relative paths for the assets.

What actually happened?

cdk synth creates references with absolute paths for the assets.

Environment

• CDK CLI Version: 1.75
• Framework Version: 1.75
• Node.js Version: v12.18.0
• OS : Ubuntu 18.10
• Language (Version): TypeScript (3.9.7)

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This is 🐛 Bug Report

[rix0rrr]

@bracki you are gold.

[bracki]

This seems like a bug in https://github.com/aws/aws-cdk/blob/master/packages/%40aws-cdk/core/lib/custom-resource-provider/custom-resource-provider.ts#L143. If I replace that line with fileName: staging.relativeStagedPath(stack) it works.