Default to "latest" version (and more)

[jcbhmr]

this pr actually kinda tackles many things at once:

1. if version is latest, replace it with latest version from https://github.com/tinygo-org/tinygo/releases
2. use more "official-y" funcs (check_packages and rm -rf /var/lib/apt/lists/*)
3. use dpkg --print-architecture which would appear(?) to print "amd64" on my x64 machine so i think just arch=$(dpkg --print-architecture) is ok? idk tho. I've been wrong before 😅
4. rm -rf /var/lib/apt/lists/* at the end

😬 idk if you want me to split this into multiple prs to selectively merge? 👆 - they just kinda happened as i replaced code 🤣

this pr would:

• if the VERSION var is "latest" ("" defaults to "latest" via ${var:-defaulttext})...
  • curl https://github.com/tinygo-org/tinygo/releases/latest
  • that redirects too https://github.com/tinygo-org/tinygo/releases/v0.29.0
  • grep (sed actually) \/v(.*)$ but print ONLY the (.*) capture group https://stackoverflow.com/a/58379307/19522682
  • use grep -oP '\d+\.\d+\.\d+$' to get that juicy version number on the end
  • set VERSION to that 1.2.3 thing
• change the arch detection to just use arch=$(dpkg --print-architecture)
• rm -rf /var/lib/apt/lists/* at the end like https://github.com/devcontainers/features do a lot
• change devcontainer-feature.json to use latest as the default instead of 0.28.1

@lee-orr this is your feature so idk if you want to change any of this at all. it works fine as-is. this is just some ideas that i had 😊.

[jcbhmr]

good news: the url properly redirects and gets printed!

jcbhmr@PIG-2016:~/Documents/23$ curl -fsSL https://github.com/tinygo-org/tinygo/releases/latest -w '%{url_effective}' -o /dev/null
https://github.com/tinygo-org/tinygo/releases/tag/v0.29.0

bad news: the sed magic to extract that last v0.29.0 part fails 😭😭

time to fix! 🔧

[jcbhmr]

back to green!

jcbhmr@PIG-2016:~/Documents/23$ curl -fsSL https://github.com/tinygo-org/tinygo/releases/latest -w '%{url_effective}' -o /dev/null | grep -oP '\d+\.\d+\.\d+$'
0.29.0

[lee-orr]

This all looks great to me!