"Block" dependent builds when a parent build is running

As discussed in the forums (copied below for completeness); allow for option to have parent builds block children. This would allow children projects to use the most recent libraries from the parent, and prevent false positive builds where the parent is broken, or breaks compatibility. A side affect is that this also makes the build sequence more efficient by not building children that would obviously fail (when parent is failing).

Original response in forum:

Basil,

So what you want is the ability to "block" dependent builds when a parent build is running? e.g.

Build A has child builds B, C and D is a child of C.

If I check into all the sources simultaneously (though obviously A has to build first), then you'd want A to build, and B & C not to build until A is finished? And D not until C is finished? Are you doing this so since the child builds uses the libraries in the their builds?
> Basil: Yes, that is correct.

Also, if A build fails, B and C would not build. Would that be okay?
> Basil: Yes that is what's expected.