angular-cli build: How can I create a custom index

Question

Currently I have an app.aspx file where I have manually copied the script tags generated from index.html file:

<script type="text/javascript">
    var serverRenderedConfigurations = {
        rootHref: "<%= Url.Content("~") %>",
        technicalHelpdeskEmail: "<%= ViewData["master.TechnicalHelpdeskEmail"] %>",
        technicalHelpdeskNumber: "<%= ViewData["master.TechnicalHelpdeskNumber"] %>"
    };
</script>

<script type="text/javascript" src="<%= Url.FreshContent("~/AngularAppOutput/runtime.js") %>"></script>
<script type="text/javascript" src="<%= Url.FreshContent("~/AngularAppOutput/polyfills.js") %>"></script>
<script type="text/javascript" src="<%= Url.FreshContent("~/AngularAppOutput/styles.js") %>"></script>
<script type="text/javascript" src="<%= Url.FreshContent("~/AngularAppOutput/scripts.js") %>"></script>
<script type="text/javascript" src="<%= Url.FreshContent("~/AngularAppOutput/vendor.js") %>"></script>
<script type="text/javascript" src="<%= Url.FreshContent("~/AngularAppOutput/main.js") %>"></script>```

I'd like the file to be generated using angular-cli build. I'm thinking about possibly passing in a custom builder + configure it in angular.json file so that instead of/along with building the index.html file my builder will be run which will generate this aspx file.

Is it possible to do this? If so, some pointers with example will be great.