index.html only updated with scripts if it contains body-tag

[NillDk]

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update
• lint
• extract-i18n
• run
• config
• help
• version
• doc

Is this a regression?

Yes, it works in Angular 10.
It doesn't work in Angular 11.

Description

We use Angular in conjunction with ASP.NET.
In our situation we want to add script-tags to a so-called partial view - a html-file not containing html- or body-tags.
This worked for us in Angular 10.
However, in Angular 11 the /dist/index.html is not updated with script-tags.

🔬 Minimal Reproduction

Create project: ng new angular11
Modify index.html to have blank content. Or at least not a body-tag.
Build: npm run build

🌍 Your Environment

Angular CLI: 11.0.1
Node: 12.18.0
OS: win32 x64

Angular: 11.0.0
... animations, common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router
Ivy Workspace: Yes

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1100.1
@angular-devkit/build-angular   0.1100.1
@angular-devkit/core            11.0.1
@angular-devkit/schematics      11.0.1
@angular/cli                    11.0.1
@schematics/angular             11.0.1
@schematics/update              0.1100.1
rxjs                            6.6.3
typescript                      4.0.5

Anything else relevant?

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