dev/sg: migrate hadolint script to sg, add shared download.Executable (!34926) · Merge requests · Administrator / sourcegraph · GitLab

Administrator requested to merge docker-lint into main May 04, 2022

Created by: bobheadxi

Migrates docker-lint.sh, which was broken, to sg
add shared download.Executable, also used by sg update
fix sg lint not printing errors

Test plan

go run ./dev/sg lint docker https://buildkite.com/sourcegraph/sourcegraph/builds/145889