[FirefoxNightly] Save downloads at an user-accessible location

[paulusasol]

Error description

I just tried downloading some files using the Nightly flatpak, however, I couldn't find them anywhere outside of the flatpak, they apparently landed inside some directory not easily accessible outside the flatpak. It is a little bit annoying being forced to redo a 3.5GiB download.

Proposed quick-fix

The easiest thing should be to add r/w filesystem access to the users downloads folder using --filesystem=xdg-download:rw so that the flatpak has access to the user's download folder.

[garrett]

Current workaround: Until a fix lands, you can run the following:

sudo flatpak override org.mozilla.FirefoxNightly --filesystem=xdg-download

...and then restart Firefox. After that, go to preferences and select your download location (and choose your normal downloads folder).

[glaubersm]

this workaround does not work with Wayland build.

[xhorak]

The -filesystem=xdg-download:rw added to the builds. Thanks.