Use a concurrency group to avoid unnecessary CI runs (#10059)
Use a concurrency group to avoid unnecessary CI runs (#10059)

Right now, we build every time someone pushes, which is quite wasteful.
There are some use cases for finishing in-progress runs because we
might be close to creating a cacheable artifact, but we don't have
those yet, and for now this should avoid a lot of unnecessary builds.

Tested: You can see the run for 07241b5088 was cancelled when I pushed
another commit fixing up some leftover debugging.
iree-org/iree,iree-org/iree,google/iree,iree-org/iree,iree-org/iree,iree-org/iree,google/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,google/iree,google/iree