gitlab-ci: force distcheck to use included GNU ltdl

* .gitlab-ci.yml: Here.
13 jobs for next in 234 minutes and 36 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed alpine-gcc #24733

00:21:30

passed arch-clang #24734

00:37:35

passed arch-gcc-glibcxxdebug #24735

00:38:00

passed debian-gcc-snapshot #24732

01:01:10

passed debian-stable-gcc #24730

00:37:32

passed debian-unstable-gcc-coverage #24731

00:35:04

88.8%
passed debpkg-stable #24738

02:29:09

passed debpkg-unstable #24739

03:40:12

passed mingw-shared #24736

00:11:54

passed mingw-static #24737

00:07:56

passed rpm-pkg #24740

00:35:27

 
  Publish
passed publish-rpm #24741
dput

00:00:18

passed publish-unstable #24742
dput

00:02:08