K3s cluster uninstall leaves some buildkit bits behind which are confusing for new Kim installation

[rreinurm]

kim version v0.1.0-alpha.12 (ac0a8eb)
k3s version v1.21.0+k3s1 (2705431d)

How to reproduce:

1. Install k3s for example with default curl -sfL https://get.k3s.io | sh -
2. Fetch kim binary and install builder kim builder install
3. Build some image kim image build --tag loca/image:my-tag . (works first time)
4. Uninstall k3s /usr/local/bin/k3s-uninstall.sh
5. Rerun steps 1-3. Building image produces error

 => ERROR [internal] load build definition from Dockerfile                                                                                                                               0.0s
------
 > [internal] load build definition from Dockerfile:
------
Error: failed to solve: rpc error: code = Unknown desc = failed to solve with frontend dockerfile.v0: failed to read dockerfile: failed to mount kkbvfei6frqlmmg4b8qssr948: snapshot kkbvfei6frqlmmg4b8qssr948 does not exist: not found
Usage ...
FATA[0000] failed to solve: rpc error: code = Unknown desc = failed to solve with frontend dockerfile.v0: failed to read dockerfile: failed to mount kkbvfei6frqlmmg4b8qssr948: snapshot kkbvfei6frqlmmg4b8qssr948 does not exist: not found 

Buildkit container produces log:

time="2021-05-19T07:09:27Z" level=warning msg="using host network as the default"
time="2021-05-19T07:09:27Z" level=info msg="found worker \"olkj8i7negxk577jluo0hyrtj\", labels=map[org.mobyproject.buildkit.worker.executor:containerd org.mobyproject.buildkit.worker.hostname:RennoRei-LenovoP1-lin org.mobyproject.buildkit.worker.snapshotter:overlayfs], platforms=[linux/amd64 linux/386]"
time="2021-05-19T07:09:27Z" level=info msg="found 1 workers, default=\"olkj8i7negxk577jluo0hyrtj\""
time="2021-05-19T07:09:27Z" level=warning msg="currently, only the default worker can be used."
time="2021-05-19T07:09:27Z" level=warning msg="TLS is disabled for unix:///run/buildkit/buildkitd.sock"
time="2021-05-19T07:09:27Z" level=info msg="running server on /run/buildkit/buildkitd.sock"
time="2021-05-19T07:09:27Z" level=info msg="running server on [::]:1234"
time="2021-05-19T07:10:15Z" level=error msg="/moby.buildkit.v1.Control/Solve returned error: rpc error: code = Unknown desc = failed to solve with frontend dockerfile.v0: failed to read dockerfile: failed to mount kkbvfei6frqlmmg4b8qssr948: snapshot kkbvfei6frqlmmg4b8qssr948 does not exist: not found\n"

Workaround

wipe out /var/lib/buildkit on the host where k3s is installed:
kim builder uninstall (can take ~30 seconds as it is deleting the namespace with all of the k8s objects kim created)
sudo find /var/lib/buildkit -mindepth 1 -delete
kim builder install