Remove some non-determinism

Your app is not built reproducible in F-Droid, but we continuously test older versions on https://verification.f-droid.org/ and would like more and more apps to become repro

Looking at the latest app report: https://verification.f-droid.org/packages/de.kromke.andreas.cameradatefolders/

Could you set TIMESTAMP in https://gitlab.com/AndreasK/camera-date-folders/-/blob/v1.5/app/build.gradle?ref_type=tags#L11 based on the last commit date instead? eg. git show --no-patch --format=%ct