Spotter-VM/vm/etc/apk/repositories

http://dl-cdn.alpinelinux.org/alpine/v3.12/main
http://dl-cdn.alpinelinux.org/alpine/v3.12/community
@vm https://repo.spotter.cz/alpine/v3.12/apk
Bump basic VM to Alpine 3.12, drop custom LXC as 3.12 uses LXC 4.0.2 2020-10-11 21:45:03 +02:00			`http://dl-cdn.alpinelinux.org/alpine/v3.12/main`
			`http://dl-cdn.alpinelinux.org/alpine/v3.12/community`
			`@vm https://repo.spotter.cz/alpine/v3.12/apk`