uv build doesn't respect SOURCE_DATE_EPOCH

[hynek]

While moving build-and-inspect-package to uv build, I noticed that you don't respect SOURCE_DATE_EPOCH (or something similar, but I believe that's a bit of a standard). baipp uses this to set the timestamp of all files to the timestamp of the latest commit, so this feature would be important for reproducible builds.

[hynek]

my bad, solved with the help of @henryiii, uv build is not responsible for any of this.