fix(ecr-assets): Fix relative path of tarball asset when using stages

[abelmokadem]

Issue # (if applicable)

N/A

Reason for this change

Docker Images can't be pushed from a staged tarball if CDK Stages are used.

This is because the relative path is not being compared against the correct directory. The current comparison is done against the assetOutDir instead of the outDir.

When a CDK app doesn't use stages, these 2 directories are the same and it works.
When a CDK app does use stages, these 2 directories are not the same and the docker tag command breaks.

Description of changes

Use outDir instead of assetOutDir.

Describe any new or updated permissions being added

N/A

Description of how you validated changes

I deployed a stack with and without Stages, before and after I made the change.

In the before, the Stage approach failed.
After the change, both versions worked.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

Your pull request must be based off of a branch in a personal account (not an organization owned account, and not the main branch). You must also have the setting enabled that allows the CDK team to push changes to your branch (this setting is enabled by default for personal accounts, and cannot be enabled for organization owned accounts). The reason for this is that our automation needs to synchronize your branch with our main after it has been approved, and we cannot do that if we cannot push to your branch.

[aws-cdk-automation]

The pull request linter fails with the following errors:

❌ Fixes must contain a change to an integration test file and the resulting snapshot.
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[aws-cdk-automation]

Your pull request must be based off of a branch in a personal account (not an organization owned account, and not the main branch). You must also have the setting enabled that allows the CDK team to push changes to your branch (this setting is enabled by default for personal accounts, and cannot be enabled for organization owned accounts). The reason for this is that our automation needs to synchronize your branch with our main after it has been approved, and we cannot do that if we cannot push to your branch.

[aws-cdk-automation]

Your pull request must be based off of a branch in a personal account (not an organization owned account, and not the main branch). You must also have the setting enabled that allows the CDK team to push changes to your branch (this setting is enabled by default for personal accounts, and cannot be enabled for organization owned accounts). The reason for this is that our automation needs to synchronize your branch with our main after it has been approved, and we cannot do that if we cannot push to your branch.