Remove automatic fallback to $HOME/.emscripten_cache. NFC

[sbc100]

Putting the cache in the $HOME directory is not a great idea since its a location that is shared by any/all versions of emscripten. If anyone really wants to use that location they can do so via the config file setting CACHE or via the environment variable EMCC_CACHE.

[kripken]

Thanks!

I imagine the link could help someone. Like imagine a dev is maintaining an emcc build that they didn't set up themselves, and it breaks due to this. They aren't a power user and just want to fix it quickly, so the more info we can give them, the better.

[neondev9]

is it really expected that emscripten compiler doesn't create --cache/EM_CACHE directories now?
i.e. if you override cache directory, you need to guarantee that directory exists before compilation.

Just updated SDK from 3.1.57 and this change affected Github Action pipelines because of
em++: error: unable to create cache directory "/home/runner/work/Project/Project/.tmp/Emscripten/cache": parent directory not writable (see https://emscripten.org/docs/tools_reference/emcc.html for info on setting the cache directory)

[sbc100]

is it really expected that emscripten compiler doesn't create --cache/EM_CACHE directories now? i.e. if you override cache directory, you need to guarantee that directory exists before compilation.

Just updated SDK from 3.1.57 and this change affected Github Action pipelines because of em++: error: unable to create cache directory "/home/runner/work/Project/Project/.tmp/Emscripten/cache": parent directory not writable (see https://emscripten.org/docs/tools_reference/emcc.html for info on setting the cache directory)

Sorry, no that was not an indented change in behaviour. Sounds like a case we don't cover in out tests.