The joined argument string is only useful for logging; some terminal
emulators seem to accept it (which probably means they pass their one
argument to a shell), others fail (gnome-terminal, alacritty, …).
By splitting the arguments, this should work on all terminal emulators.
Tested against xterm and alacritty, the former still works, the latter
now works.
Signed-off-by: Marcus Müller <mmueller@gnuradio.org>