Build-image: Switch to rbenv or asdf-vm instead of RVM

[bcomnes]

In general, it seems most people are not a fan of rvm (it does weird things like override default unix command... or did at one point? Not sure anymore), and it's been a constant headache to keep working.

I was thinking of switching the ruby version manager over to

• https://github.com/rbenv/rbenv
• https://asdf-vm.com/#/

Rbenv is well liked by most Rubyist I've asked, but asdf would offer a uniform package manager for pretty much every language we support, which is appealing.

Have an opinion? Let me know here, otherwise I'll likely just choose one.

[elisehein]

+1 from me for asdf. Some of our projects on netlify use both ruby and node, and it would be nice to be able to specify both runtime versions in .tool-versions.

[bcomnes]

I considered adding it for python a while back since we didn't have a good version manager story for that yet. It turns out no python version manager can download prebuilt pythons! They all require build-from-source install.

asdf could still possibly work for ruby, node and anything else that doesn't require a build-from-source install.