Emscripten settings in configure.ac are not embedding friendly

Bug report

Bug description:

I would like to be able to opt out of certain Emscripten options since I am embedded CPython in a larger application. For example, the forced inclusion of the JS file system is breaking my builds since I use WASMFS in my system which isn't compatible with -lidbfs.js, -lnodefs.js, -lproxyfs.js, -lworkerfs.js. Moreover, I would like to customise the TOTAL_MEMORY option.

Perhaps these options can be on by default but placed behind a flag that can turn them off? For example, --enable-wasm-emscripten-jsfs? Alternatively, perhaps all these settings can be disabled unless one of node, browser, node-debug, browser-debug is set via --with_emscripten_target?

Right now, it seems my only option is to apply a patch to turn these settings off which should be unnecessary in my opinion. @hoodmane @vstinner what do you think?

CPython versions tested on:

CPython main branch

Operating systems tested on:

Other

Beginne damit, configure.ac um die Zeilen 2340–2351 und die bestehende Behandlung von --with_emscripten_target zu lesen. Ermittle, wie die Emscripten-JavaScript-Dateisystemoptionen und TOTAL_MEMORY derzeit gesetzt werden, und definiere anschließend, wie eingebettete Builds sie deaktivieren oder anpassen können. Als erledigt gilt die Aufgabe, wenn die angeforderten Einstellungen gesteuert werden können, ohne einen Patch pflegen zu müssen.