OCI build throws cache error, but proceeds

[dtrudg]

E.g.

02:58 pm $ singularity build --oci /tmp/myimage.oci.sif Git_Sylabs/singularity/examples/nested/Dockerfile 
INFO:    Did not find usable system buildkitd daemon. Starting built-in singularity-buildkitd.
INFO:    singularity-buildkitd: running server on /run/user/1000/singularity-buildkitd/singularity-buildkitd-86109.sock
[+] Building 0.0s (0/1)                                                                                                 
 => [internal] load build definition from Dockerfile                                                               0.0s
ERRO[0001] gc error: no such file or directory
could not stat fs at 
github.com/moby/buildkit/util/disk.GetDiskStat
	github.com/moby/buildkit@v0.27.1/util/disk/disk_unix.go:14
github.com/moby/buildkit/cache.(*cacheManager).prune
	github.com/moby/buildkit@v0.27.1/cache/manager.go:1067
github.com/moby/buildkit/cache.(*cacheManager).Prune
	github.com/moby/buildkit@v0.27.1/cache/manager.go:1019
github.com/moby/buildkit/worker/base.(*Worker).Prune
	github.com/moby/buildkit@v0.27.1/worker/base/worker.go:507
github.com/moby/buildkit/control.(*Controller).gc.func2
	github.com/moby/buildkit@v0.27.1/control/control.go:656
golang.org/x/sync/errgroup.(*Group).Go.func1
	golang.org/x/sync@v0.19.0/errgroup/errgroup.go:93
[+] Building 0.6s (2/2)                                                                                                 
 => [internal] load build definition from Dockerfile                                                               0.0s
[+] Building 18.5s (6/6)                                                                                                
[+] Building 18.6s (6/6) FINISHED                                                                                       
 => [internal] load build definition from Dockerfile                                                               0.0s. => => transferring dockerfile: 690B                                                                               0.0s
 => [internal] load metadata for docker.io/library/ubuntu:25.04                                                    0.6s
 => [internal] load .dockerignore                                                                                  0.0s
 => => transferring context: 2B                                                                                    0.0s
 => CACHED [1/2] FROM docker.io/library/ubuntu:25.04@sha256:27771fb7b40a58237c98e8d3e6b9ecdd9289cec69a857fccfb85f  0.0s
 => => resolve docker.io/library/ubuntu:25.04@sha256:27771fb7b40a58237c98e8d3e6b9ecdd9289cec69a857fccfb85ff36294d  0.0s
 => [2/2] RUN ln -s /usr/share/zoneinfo/UTC /etc/localtime &&     apt-get -yq update &&     apt-get -yq install   11.0s 
 => exporting to docker image format                                                                               6.9s 
 => => exporting layers                                                                                            6.6s 
 => => exporting manifest sha256:8b63ea40dc66c861ce72aa0592815dfdfcb0c7a70807a76015c054b27a25ea05                  0.0s 
 => => exporting config sha256:eff9c5f9d47972b25970f1324d00fdd44cd0db73efc2a650c600da8df910453d                    0.0s 
 => => sending tarball                                                                                             0.3s 
INFO:    Converting layers to SquashFS
INFO:    Cleaning up.
INFO:    Terminating singularity-buildkitd (PID 86149)
INFO:    Build complete: /tmp/myimage.oci.sif