switch Linux build over to use configured docker image

[shiftkey]

Description

Extracting out from #897 to just focus on shifting the Linux builds over to using Docker (with an earlier version of Ubuntu and a different node that supports an older glibc).

[theofficialgman]

not sure if you intend on fixing all the cross compilation issues in this PR but you are missingthe dist-info.ts and build.ts script changes
https://github.com/shiftkey/desktop/pull/897/files#diff-bedccfa88bfc1b5eb66ff5bb37b320e3bbf3819f61b10b95c00ee58f0da58baf
https://github.com/shiftkey/desktop/pull/897/files#diff-8f5152cdb50c1fff0034a810c976a72398933e3e4680f3fb52a3e60bb27e172f

implement however you want as long as the function is the same. your changes here are a nice cleanup, I hadn't thought of that (was just following the previous work) aff1c2b

[shiftkey]

@theofficialgman 👍🏻 about to push that fix now

[theofficialgman]

can't comment high enough. look up a few lines, in the file I refererenced to you. you need to change

 if (
      targetArch === 'arm64' ||
      targetArch === 'x64' ||
      targetArch === 'armv7l'
    ) {
      return targetArch
    }

its input is npm_config_arch and armv7l isn't valid input. arm is but the returned value needs to be armv7l (for electron packager)

[theofficialgman]

actually nvm. the functionality as it is will work, it will just be impossible to hit targetArch === 'armv7l' since npm_config_arch should never contain that and os.arch will never return that

[theofficialgman]

also just an fyi, I can't mark any of these reviews as resolved. only you (the repo owner or the PR owner, in this case you are both) can do that