Repository: godot
Issue: Exporting a C# project with the standard version won't raise an error
Labels: bug,topic:dotnet,topic:export

### Godot version

3.4.4

### System information

Windows 10, or a github action linux runner

### Issue description

I'm developing a setup godot github action, and just recently added the option for the mono version of godot.

When trying to test it, I expected for godot to exit with an error when trying to export a C# project with the standard version, but that's not the case. It exported a HTML5 preset with all the files, but the game won't run. It stays frozen in the first frame of the game.

This kind of behaviour is not very derisable for CI/CD. Might be better to exit with error when trying something like this.

### Steps to reproduce

Pre-requisites:
- Godot 3.4.4 standar version
- Python or any other way to serve the html file without your browser giving a CORS error

Steps:
- Clone the repository https://github.com/Vitorgus/Godot-Deploy-Test-Mono , which is basically the official pong with c# official demo with a HTML5 template. Or open a c# project of your own and create a HTML5 template
- Navigate to the cloned folder
- Create a `build` dir
- Run `<godot> -v --export "HTML5" ./build/index.html`, where `<godot>` is the path to the godot 3.4.4 standard executable
- Go to the `build` dir
- Start the server
  - Python 3: `python3 -m http.server`
  - Python 2: `python -m SimpleHTTPServer`
  - Or any other way you prefer
- Open the server url, and the game won't move


### Minimal reproduction project

I've made a repository to test it, it's a clone of the official pong with C# demo: https://github.com/Vitorgus/Godot-Deploy-Test-Mono

This game is currently deployed with the export error in the following url: : https://vitorgus.github.io/Godot-Deploy-Test-Mono/

The github action for the export generated the following log:
```
Godot Engine v3.4.4.stable.official.419e713a2 - https://godotengine.org/
CORE API HASH: 4983981888327659428
EDITOR API HASH: 17985513469441247513
Construct gdnative interface
Destruct gdnative interface
Class 'BulletPhysicsDirectBodyState' is not exposed, skipping.
Class 'BulletPhysicsDirectSpaceState' is not exposed, skipping.
Class 'BulletPhysicsServer' is not exposed, skipping.
Class 'GDScriptNativeClass' is not exposed, skipping.
Class 'IP_Unix' is not exposed, skipping.
Class 'InputDefault' is not exposed, skipping.
Class 'Physics2DDirectBodyStateSW' is not exposed, skipping.
Class 'Physics2DDirectSpaceStateSW' is not exposed, skipping.
Class 'Physics2DServerSW' is not exposed, skipping.
Class 'ResourceImporterMP3' is not exposed, skipping.
Class 'ResourceImporterOGGVorbis' is not exposed, skipping.
Loaded builtin certs
EditorSettings: Save OK!
savepack: begin: Packing steps: 102
	savepack: step 2: Storing File: res://.import/ball.png-9a4ca347acb7532f6ae347744a6b04f7.stex
	savepack: step 2: Storing File: res://ball.png.import
	savepack: step 22: Storing File: res://.import/icon.png-487276ed1e3a0c39cad0279d744ee560.stex
	savepack: step 22: Storing File: res://icon.png.import
	savepack: step 42: Storing File: res://.import/paddle.png-0e798fb0912613386507c9904d5cc01a.stex
	savepack: step 42: Storing File: res://paddle.png.import
	savepack: step 62: Storing File: res://pong.tscn
	savepack: step 82: Storing File: res://.import/separator.png-f981c8489b9148e2e1dc63398273da74.stex
	savepack: step 82: Storing File: res://separator.png.import
	savepack: step 102: Storing File: res://icon.png
	savepack: step 102: Storing File: res://project.binary
savepack: end
EditorSettings: Save OK!
```