Use commit date in release binary artifacts

[aciba90]

Use the commit date of the HEAD commit as date for the release binary artifacts date maintaining determinism but being realistic.

Previously, a constant 2015-10-21 00:00Z was used.

Fixes #2007

Signed-off-by: Alberto Contreras [email protected]

[aciba90]

I have tested it by:

make release   # with containerd-snapshtter set as true

$ git show -s --format='%cI' HEAD
2025-06-18T18:38:27+02:00

$ tar tavf bin/release/buildkit-v0.23.0-rc1-5-gdb4643606.linux-amd64.tar.gz 
drwxr-xr-x root/root         0 2025-06-18 18:38 bin/
-rwxr-xr-x root/root  33414304 2025-06-18 18:38 bin/buildctl
-rwxr-xr-x root/root   5694447 2025-06-18 18:38 bin/buildkit-cni-bridge
-rwxr-xr-x root/root   5749447 2025-06-18 18:38 bin/buildkit-cni-firewall
...

# both dates are aligned

rm -rv bin/release/*  # and repeat the process, verify the date is still the same

[crazy-max]

Seems tarball is not created :thinking:: https://github.com/moby/buildkit/actions/runs/15738588557/job/44462990343?pr=6037#step:3:16

Maybe artifacts got pruned when re-running the workflow. Let me do a full re-run to make sure.