Meson port removed option to build without a session manager

Prior to the meson port, you could explicitly disable all session managers (--without-systemd --without-elogind --without-console-kit). However, the Meson port introduced a combo option session-manager that doesn't take none for an answer:

option( 'session-manager', type: 'combo', choices: ['systemd', 'elogind', 'consolekit'], value: 'systemd', description: 'Session manager', )

As such, it is no longer possible to build without any session manager support.