Remove repo zip + unzip steps from CI bulds

[mmitche]

https://dev.azure.com/dnceng/public/_build/results?buildId=430659&view=logs&j=9269f66d-1f85-5c3b-5cd1-c24f22859cb8

I believe this was added to workaround the throttling that was happening when building coreclr. Since this got fixed via a network reconfiguration on the GitHub side, this can probably be removed.

[ViktorHofer]

cc @trylek @jashook @jkoritzinsky

[jkoritzinsky]

The repo zip/unzip steps have also enabled the coreclr builds to all use the same merge commit. We were having issues beforehand where the product build would use one commit and the test would use a later one if someone merged a PR in the middle, sometimes leading to confusing extraneous test failures.

[trylek]

I also believe @echesakovMSFT has a working change about to port to the runtime repo that further improves on this logic by replacing zipping / unzipping with git bundles which should be cleaner and remove the need for two different checkouts on Windows / Linux.

[mmitche]

The repo zip/unzip steps have also enabled the coreclr builds to all use the same merge commit. We were having issues beforehand where the product build would use one commit and the test would use a later one if someone merged a PR in the middle, sometimes leading to confusing extraneous test failures.

That should not happen and is a bug in AzDO if it does. Assuming that they are being run in the same pipeline, the specific merge sha should be being passed around. If that is not the case, then that is a serious bug that we should not workaround.

We should really get rid of this workaround.

[trylek]

OK, if you say this should now work correctly and throttling is no longer a problem, I can easily prepare and test a change to remove the repo zipping / unzipping.