Do not define DEBUGINFOD_URLS directly.

We're retaining the core file now and starting with bullseye, gdb takes
a long time to retrieve all symbols on startup which messes with tests.
3 jobs for !446 with gitlab-ci in 51 minutes and 54 seconds (queued for 8 seconds)
detached
Status Name Job ID Coverage
  Build
passed build-gnutls-mit-standalone-lloadd #10212

00:43:40

passed build-no-threads-no-slapd #10210

00:03:29

passed build-openssl-heimdal-lloadd #10211

00:50:14