[3.24] build: Define USE_XDG_ACTIVATION conditional when Wayland is disabled
This fixes Autotools builds that disable Wayland, such as non-Linux operating systems and the minimal "udeb" (micro-.deb) package used in Debian's installer.
This fixes Autotools builds that disable Wayland, such as non-Linux operating systems and the minimal "udeb" (micro-.deb) package used in Debian's installer.