add Github action to verify that every commit in a PR compiles on its own
add Github action to verify that every commit in a PR compiles on its own

When rebasing a PR with multiple commits; it's tedious to checkout each commit
and ensure the code builds fine.

This GitHub action checkout and builds every commit in a PR.

Fixes: #12554

Signed-off-by: Ankur Kothiwal <5b2dcd4ef7c4f903f281cd735b9968beed2454aa@accuknox.com>

michi-covalent/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,tklauser/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,tklauser/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium