Upgrade base box to Bullseye

[ocdtrekkie]

I think we need to address #330 before we merge this, and I also am going to do some testing against our test packages yet. We still need good test packages for some stacks (#298), which is also arguably blocking #290.

This also fixes #255. Node 14 is a supported LTS releae, and node-capnp supports Node 14, so we'll bump that up to be relatively modern as well.

[ocdtrekkie]

PHP test app is good, I submitted fixes for other issues unrelated to the base box upgrade.

Python stack is currently broken, with default: E: Package 'python-virtualenv' has no installation candidate. I think it's probably a safe assumption that's a Python 2 vs. 3 issue, which means we probably need to update our sample app for Python 3. I'm not looking at that tonight, but I'll document it here as a blocker to merging this PR.

[ocdtrekkie]

Okay, @zenhack, this is ready for your review. Note that on my Windows box, I had to run virtualenv --copies in build.sh to avoid the symlink issue, but I don't feel we should change that by default because it can be very wasteful in packaging output.

sandstorm-io/python-app-to-package-for-sandstorm#4 is the simultaneously-needed update to our test app.

[ocdtrekkie]

Hmmm, I just pushed that last commit on here for Node, before realizing we waited last time until node-capnp was supported. I don't think apps actually necessarily need node-capnp, and we don't currently have a test app either for that stack, so I think for the moment, I would be in favor of just keeping current as Node 14 goes EOL in a handful of months, and we push actual vagrant-spk releases rarely.

[zenhack]

LGTM.

I agree with keeping node current, rather than waiting for node-capnp to catch up.