Now that our process-launching internals are identical between the
(still-misnamed) weston_client_launch and the frontend's Xwayland
launcher, we can reuse the internals instead of open-coding it.
As a result, we now additionally prevent Xwayland from inheriting
Weston's signal mask, by clearing SIG_UNBLOCK on all signals. This
should have no observable effect as we do not depend on signal handling
within Xwayland, instead using the displayfd readiness mechanism since
c2f4201ed2a8.
Signed-off-by: Daniel Stone <daniels@collabora.com>
3ac2748021