global: Remove BUILD_DATE and BUILD_TIME

All this does is make reproducible builds impossible.
3 jobs for no-build-date-time in 12 minutes and 30 seconds (queued for 3 minutes and 24 seconds)
Status Job ID Name Coverage
  Docker Image
passed #508362
debian-testing

00:00:21

 
  Build And Test
passed #508363
autotools-build-and-test

00:09:14

passed #508364
meson-build-and-test

00:04:15