SINGLE_FILE and pthread incompatibility

According to https://github.com/emscripten-core/emscripten/pull/12833#issue-746884561 which says the following:

> SINGLE_FILE=1 is not supported with Wasm Workers (like it is not supported with pthreads)

I'm unable to find other specific documentation for pthreads not supporting SINGLE_FILE, but locally I can confirm that removing SINGLE_FILE does indeed fix the threading issue I'm running into (where the thread does not get executed with `detach`).

What is the specific reason(s) that SINGLE_FILE does not work with pthreads? From what I understand about SINGLE_FILE, it adds the contents of the .js and .wasm files (as a Base64 string) into the HTML file as opposed to reading the wasm contents via locateFile - clearly there is something else that I'm missing.

Empieza leyendo el pull request de Emscripten enlazado y comparando el comportamiento de pthreads informado con y sin SINGLE_FILE=1. Sigue cómo interactúan SINGLE_FILE, locateFile y Wasm Workers en los puntos de entrada relevantes de Emscripten. Se considera terminado cuando se documenten las razones específicas por las que SINGLE_FILE es incompatible con pthreads y se aclare la configuración compatible.

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