CI should build with Meson
@pavlosun Pavlo, you introduced CI in glibmm with MR !24 (merged). The .gitlab-ci.yml file will need updating. No hurry, but some time in the future. It would be fine, if you could do that. Like I said in your MR, I don't know much about CI, and I prefer not to spend much time learning it.
The CI file builds libsigcplusplus and glibmm with autotools (autogen.sh + make). Both libsigcplusplus and glibmm can now be built with meson. Autotools support will probably be dropped in the future. CI should build with meson. Alternatively, it can build glibmm with both autotools and meson. The two builds should then be well separated, so it will be easy to remove the autotools build when autotools support si dropped.
What versions of libglib2.0-dev and mm-common are installed by the CI file? Will they always (or at least usually) be recent enough? The latest glibmm patches in the git repo often use new glib API before it has been included in a released glib version.