GitLab CI: APT package updates.

Don't pass "-Zgzip" to dpkg-buildpackage on Ubuntu. Newer versions
default to zstd. Pass "-zfast" to dpkg-buildpackage on Debian and use
ccache.

.gitlab-ci.yml

@@ -214,7 +214,7 @@ Debian Stable APT Package:
     - export DEB_BUILD_OPTIONS="nocheck parallel=$(( $(getconf _NPROCESSORS_ONLN) + 2 ))"
     - export DH_QUIET=1
     - export MAKEFLAGS=--silent
-    - dpkg-buildpackage -b --no-sign -jauto
+    - CC=/usr/lib/ccache/gcc CXX=/usr/lib/ccache/g++ dpkg-buildpackage -b --no-sign -jauto -zfast
     - lintian --suppress-tags library-not-linked-against-libc,copyright-excludes-files-in-native-package --display-experimental --display-info --pedantic --profile debian
     - mkdir debian-packages
     - mv ../*.deb debian-packages/
@@ -296,7 +296,7 @@ Ubuntu APT Package:
     # build-ubuntu puts us in `build`.
     - cd ..
     - ln --symbolic --no-dereference --force packaging/debian
-    - CC=/usr/lib/ccache/gcc CXX=/usr/lib/ccache/g++ MAKE=ninja dpkg-buildpackage -us -uc -rfakeroot -jauto -Zgzip -zfast
+    - CC=/usr/lib/ccache/gcc CXX=/usr/lib/ccache/g++ MAKE=ninja dpkg-buildpackage -us -uc -rfakeroot -jauto -zfast
     - mkdir ubuntu-packages
     - mv ../*.deb ubuntu-packages/
   after_script: