Shared Pipeline Variables not exported in custom image

[fo_connor]

Hi, 

I'm testing the Output Variables feature in Bitbucket Pipelines. My pipelines use a custom in-house runtime Docker image.

My main use-case uses a mix of parallel and manual steps, but even when I try a very simple example - the variable is not carried over between steps:

  custom:

    Simple Example:

      - step:

          name: Build and Deploy

          script:

            - export MY_VAR="Hello, World!"

            - echo $MY_VAR

          output-variables:

            - MY_VAR

      - step:

          name: Use Output Variable

          script:

            - echo $MY_VAR # This is empty in the UI when running