This is one of the binaries distributed with the kubectl snap, but it’s never added to /snap/bin.
It’s required for authentication against gcr when doing docker pushes. I’m currently working around it by symlinking from the snap folder, but it obviously changes path every time the snap updates.
The kubectl snap authors likely just need to add an app for the docker-credential-gcloud binary to the snapcraft.yaml and push an update then it will show up in /snap/bin.
Only apps explicitly declared in the apps section of the snapcraft.yaml will show up in /snap/bin. Also note that the apps in /snap/bin are not mere symlinks to the binaries inside /snap/kubectl/current/..., the apps in /snap/bin are really symlinks to /usr/bin/snap, which executes the binaries inside /snap/kubectl/current/, etc. using /usr/lib/snapd/snap-exec
