ExternalProject: No dependency between patch and update steps
In !1178 (merged) it was discovered that there appears to be no dependency between the patch
and update
steps. This leaves the order of patching/updating at the mercy of the build tool and even permits both to run at once, which would be likely to cause problems. The documentation was recently updated in !1037 (merged) to state that patching is done after updating, but the old documentation did not specify an order. We should decide what the correct order is, then ensure the implementation and documentation are consistent with that. I'm happy to do the work once a decision is made about the correct behaviour.