prevent adding more binaries

[thestinger]

We keep adding test/library binaries to the history, and it's already quite large. It should just be prevented on the build bots, excluding ones intentionally added to a list of exceptions.

It's too late to remove the old ones from the history, but not too late to avoid adding more 10MiB binaries everyone has to clone.

[alexcrichton]

Oh dear, sorry about that!

I think I've done this more than once, and I'd love to have a way to prevent this. I know we can't install hooks by default, but it would also be nice to have a hook script with instructions of how to use it somewhere in perhaps src/etc.

[huonw]

We can add hooks to the buildbot/build scripts themselves though? (e.g. put something in tidy that checks for checked-in-binaries.)

[alexcrichton]

Now that you mention it, I think that tidy would be an excellent location for this.