build.yml: use sr.ht 3.11 repository

build.yml: prefer abuild -r over abuild -R

build.yml: use alpine 3.11

Add option to pass -R to abuild

Remove now-upstream packages, update to 3.10

Update build.yml with Alpine version

Use Alpine 3.9 image

Add terrible bashisms because builds.sr.ht is dumb

Minor tweaks to build.yml

Move build.yml/submit-builds to top level