What is the problem you're trying to solve

ctr produces a cryptic error when a relative path to a shim binary is specified as --runtime=./relative/path/to/shim/binary.

$ sudo ctr run  --rm --runtime=./containerd-shim-runc-v2 docker.io/library/hello-world:latest hello-world
ctr: failed to start shim: start failed: : exec: "/": permission denied: unknown

Probably ctr is attempting to parse the path string as an <TLD>.<VENDOR>.<RUNTIME>.<VERSION> format string.

An absolute path works as expected.

Describe the solution you'd like

Make the error message less cryptic.

Additional context

v1.6.0-rc.1