Just some small refactorings stemming from #3073.
AddCheckLines -> BuildCheckLines because the two lists are now fully
separate. Adding is_blank to be more direct about behavior than the
Print call.
I've migrated the toolchain autoupdate scripts here, I just need a
little more time to do the explorer side (which I need to check
performance, that may require multithreading as we do in the current
script). However, this felt substantial enough to share and it means I
can handle autoupdate in more of the toolchain, including preparatory
work for autoupdate on multi-file tests.
Once explorer is done I'll remove the old script.
Jon Ross-Perkins