Missing submodule error handling does not work in a multithreaded build in Unity 6.5 and newer

Steps to reproduce:

1.  Create empty Unity project in Unity 6.5 or newer
2. Install package "com.unity.web.stripping-tool@1.3.0"
3. Switch Platform to "Web"
4. In "Player Settings > Publishing Settings" enable
5. Enable Submodule Stripping Compatibility
6. Native C/C++ Multithreading
7.  Build project
8.  Open "Window > Web Optimization > Submodule Stripping"
9. Select the last build
10. Set "Missing Submodule Error Handling" to "Log Error"
11. Select any submodule for stripping
12. Click on "Strip & Run"

Actual results: The build runs without errors in the console.

Expected results: There are multiple errors in the console that "function.json" and "labels.json" can not be loaded.

Reproducible with versions: 6000.5, 6000.6, 6000.7

Not reproducible with versions: 6000.3, 6000.4

Can’t test with versions: 6000.0 (does not support submodule stripping package)

Tested on (OS): Windows 11

Notes:

•  This is an issue caused by the Emscripten 4 update. Module["ENVIRONMENT_IS_PTHREAD"] was renamed to just ENVIRONMENT_IS_PTHREAD