x11-clocks/wlclock: unbreak build with clang 15

../src/output.c:22:18: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
static void noop () {}

^
 void

../src/wlclock.c:578:23: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
static void clock_run ()

^
 void

Reported by: pkg-fallout