Link to error line on build output page

Build detail page command listing already has anchors for all of the lines and commands. We could add a helper to jump to the command/line that errored out, as sometimes users don't seem to scroll down on the page.

Also worth noting that some old builds have not super helpful error messages, which are just the last failed command output. These specifically could use this feature instead, though hopefully views of old builds aren't frequently viewed.

• Add an element to jump to the errored command or command line on the build detail page
• Same, but in the error notification? I don't know if we want to get into Knockout inside notifications though.

Start at the build detail page's command listing and inspect the existing anchors for lines and commands. Add a way to jump to the command or line associated with the error; decide separately whether the error notification is in scope, and verify the link lands at the failed output.