fix(aws): Only set bucket var when creds are available (#136)

The `dockerBuildWrapper` script enables caching based on the `AWS_BUCKET`
environment variable. When calling the `libp2p ping interop test` with a bucket
name but no AWS credentials, this leads to the script enabling caching even
though the workflow does not have access to AWS.

With this commit the environment variable `AWS_BUCKET` is only set when
credentials are available and thus the `dockerBuildWrapper` script does not enable
caching then workflow does nothave access to AWS.

.github/actions/run-interop-ping-test/action.yml

@@ -28,7 +28,8 @@ inputs:
 runs:
   using: "composite"
   steps:
-    - run: |
+    - if: inputs.s3-access-key-id != '' && inputs.s3-secret-access-key != ''
+      run: |
         echo "AWS_BUCKET=${{ inputs.s3-cache-bucket }}" >> $GITHUB_ENV
         echo "AWS_REGION=${{ inputs.aws-region }}" >> $GITHUB_ENV
       shell: bash