Makefile.inc1: Make package timestamps reproducible

[emaste]

Summary

Set package archive timestamps based on most recent source commit timestamp.

Suggested by: bapt

[emaste]

I'd like to record the timestamp in a file that we can include in src tarballs so that we can reproduce the build w/ hash, timestamp etc. without having to build from a git repo but there are details to sort out (D48718 proposes adding the timestamp to vers.c). @bapt suggested the approach in this review and it's a good interim improvement.

[emaste]

Makefile.inc1

601

git -C (rather than --work-tree) was the necessary bit to support worktrees

[allanjude]

Looks good

[emaste]

@allanjude thanks for looking, sorry I missed your Reviewed by