Port to Meson build system
Following the bugzilla issue, this is the updated port to meson build system.
Unfortunately, due to the existence of a couple of issues in meson's 0.46 and 0.47 versions, it's not fully usable.
Using a workaround I have been able to build
gnome-online-accounts fully with 0.47, so the issue has already been notified, and it can be used once it is solved.