termux_step_install_service_scripts is run after
termux_step_post_make_install and loops over the new array
TERMUX_PKG_SERVICE_SCRIPT to add service scripts for termux-services.
The service scripts are usually only a one-liner so we might just as
well define it in a variable like TERMUX_PKG_SERVICE_SCRIPT.
TERMUX_PKG_SERVICE_SCRIPT should be an array on the format
("daemon-name" 'script to execute' "another daemon" 'multi\n line\n script'),
i.e. it should be of even length with name + script where the script
part preferably is within single quotes (to avoid accidental expansion
of for example $HOME).
