xwayland: actually use Xwayland from pkg-config
xwayland: actually use Xwayland from pkg-config

eec2e1d3b16ba40c85483badcc7809277274ce5d introduced logic to use the Xwayland
binary discovered via pkg-config.
While the newly introduced checks correctly used the binary from pkg-config,
the actual execution still used the previous PATH-search logic.

SirCmpwn/wlroots,swaywm/wlroots,swaywm/wlroots