build: fix commit that changed option for installing client
build: fix commit that changed option for installing client

Without this patch the option --enable-demo-clients-install does not
install the client demos.

kwm81/weston,mchalupa/weston,eyolfson/weston,eyolfson/weston,Tarnyko/weston-xdg_surface_present,jonnylamb/weston,Fantu/compositor-spice,udoprog/weston,xorgy/weston,Fantu/compositor-spice,kwm81/weston,udoprog/weston,krezovic/weston,giucam/weston,Gnurou/weston,jonnylamb/weston,krezovic/weston,giucam/weston,sir-murray/weston,mchalupa/weston,Tarnyko/weston-xdg_surface_present,Fantu/compositor-spice,sir-murray/weston,xorgy/weston,Gnurou/weston