Support installing runtime into ~/.local/share

[PeterCxy]

It would be nice if a world-writable /usr/share/firefoxpwa/runtime is not a hard requirement for using this extension. It may (for example) fall back onto downloading and installing the runtime into the user-accessible directory ~/.local/share instead.

[filips123]

Currently you can only modify runtime directory by changing the source code. If you want to change just runtime directory, you need to change this line, if you want to check all installation directories, check this comment for instructions.

I will probably allow configuring this (either with some compile-time or run-time option) in the future, along with other requests abot configuring installation directories and properies (#6, #17, #24).

[PeterCxy]

Thanks. For now I've patched the code in my AUR package to move the runtime installation directory to ~/.local/share/firefoxpwa/runtime. Package managers generally like it better when the packaged program do not write to /usr (except /usr/local) directly, so supporting this as an option would make packaging it cleanly a bit easier. (However, adding a compilation option for this would require the ability to parse the ~ syntax and replace it with the HOME env variable depending on the path string provided as the option, which may require using build.rs).

[filips123]

Starting with df05306, runtime will be installed into user directory by default.

If anyone wants to change it back or use other locations, I added few comments in the code. It is still required to change the source code as using build-time env vars would complicate things, but I might change this in the future.