Reproduction steps:
1. Open the user's attached project ("My Project 001") on the WebGL platform
2. Make sure that "Project Settings -> Player -> Publishing Settings -> Enable Native C/C++ Multithreading" is checked (For Unity 2021 and 2022, check notes)
3. Build the project
Expected result: The project gets built
Actual result: The Build fails after some time with an error message (Check notes)
Reproducible with: 2021.3.34f1, 2022.3.19f1, 2023.3.0b7
Reproducible on: macOS 14.2.1 (Intel), Windows 11 (User)
Not reproducible on: No other environment tested
Notes:
1. For Unity 2021 and 2022, a script needs to be used to enable multithreading. Download the attached "Editor" archive and extract it in the Assets folder. The script's directory should be "Assets/Editor/Threads.cs"
2. The error message:
Internal build system error. BuildProgram exited with code 1.
System.ArgumentException: Another action is already registered for fdgdfgdfg/Build/d41d8cd98f00b204e9800998ecf8427e.js.unityweb
3. The user reports that the Editor might sometimes crash during building. I was not able to reproduce any crashes and none are present in the logs provided by the user