To be able to skip updaing Git submodules

### Before opening, please confirm:

- [x] I have checked to see if my question is addressed in the [FAQ](https://github.com/aws-amplify/amplify-hosting/blob/master/FAQ.md).
- [x] I have [searched for duplicate or closed issues](https://github.com/aws-amplify/amplify-hosting/issues?q=is%3Aissue+).
- [x] I have removed any sensitive information from my code snippets and submission.

### Amplify Hosting feature

Build settings

### Is your feature request related to a problem? Please describe:

Currently amplify is updating Git submodules when .gitmodules is present in the project. Currently we are not having any configuration or workaround to skip this step

Looking for an environment variable/configuration which would help to skip the step of updating submodules.

### Describe how you'd like this feature to work

Looking for an environment variable/configuration which would help to skip the step of updating submodules.

Start by tracing the Amplify Hosting build-settings flow that detects .gitmodules and updates Git submodules. Determine where an environment variable or configuration option could control that step, then verify that builds can skip submodule updates while retaining current behavior by default.

Written by the indexing model from the issue text.