Using remote builds with buildbarn

[gfleury]

Using remote builds with buildbarn (bb-deployment with docker-compose)

Changes were made accordingly to existing project already using please, so they might be biased (wrong).
So, these changes are more like questions.

• Ignore symlinks while checking outputs. This one seems a legit fix.

• Use sri.checksums only if just one hash is available. bb-remote-asset currently only takes one hash and I could not find anything defining if multiple hashes are good or not.

• Entrypoints checks on outputs considering OutputPaths. Currently we have multiple targets with entrypoints, and some have outs and other output_dirs. The ones with output_dirs seems to forced to have these dirs in the entrypoints path.

[peterebden]

Thanks for this! Nice to know the remote execution subsystem is getting exercised by others as well :D

I think the other two parts make a lot of sense but the subresource integrity change is a bit of an issue. I'm pretty sure we do take advantage of it as is; I also think that it's pretty misleading if one hash applies SRI but two hashes suddenly don't.
I do think the format should be fine though, per MDN:

Note: An integrity value may contain multiple hashes separated by whitespace. A resource will be loaded if it matches one of those hashes.

I assume we could get in touch with Ed about having bb-remote-asset support multiple values?