Bundeling takes long time to deploy

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## This issue is a:

- Bug / Performance improvement

### Environment

| Question | Answer |
| --------------------------- | :-----------: |
| Magento version | 2.2.6 |
| node.js version (`node -v`) | v6.11.1 |
| npm version (`npm -v`) | 3.10.10 |

## Description

This shop has 4 themes (which inherent from the same theme) and 2 languages. We see a huge increase in deployment time when the Javascript bundeling is enabled.

Normal deployment, without the Javascript bundeling enabled takes about 10 minutes. With Javascript bundeling enabled it takes more then 40 minutes. So bundeling and running uglify over the files increases the deployment time substantially with 30 minutes.

## Expected result:

I expect to see a light increate in deployment time, because you are adding more steps to the deployment. But an increate 3 times is a bit much.

## Possible solutions:

I see the uglify is stuck on the Javascript of the Magento_Swagger module for quite some time.

## Log files

Log files of deployment. Bundeling occurs in the step "magento:bundle" at 05:20 ends at 35:07. So takes close to 30 minutes.

[pipelineLog-581.txt](https://github.com/magento/m2-devtools/files/2778729/pipelineLog-581.txt)

Start with the attached pipelineLog-581.txt and the “magento:bundle” deployment step, comparing the bundling and Uglify timings with the non-bundled deployment. Investigate the reported delay around Magento_Swagger and consider the work complete when bundling no longer adds the reported excessive deployment time without changing the generated assets.

Written by the indexing model from the issue text.