Store xbuildenv folders in the xdg-cache directory

[agriyakhetarpal]

maybe we should put the xbuildenv folders in the xdg-cache directory. I have so many redundant xbuildenv folders on my computer.

Originally posted by @hoodmane in pyodide/pyodide#3851 (comment)

[agriyakhetarpal]

I've opened a new issue to track this, and it makes sense to me. Though, I would suggest using platformdirs's user_cache_dir location for a cross-platform option.

[hoodmane]

Thanks!

[ryanking13]

Sounds good to me. I think it would be useful to support both a global directory and local directory though, similar to venv or node_modules.