wayland-shm: Don’t set SIGBUS handlers on unshrinkable fd
If a client set the F_SEAL_SHRINK seal on the fd before passing it to the compositor, the kernel will ensure this fd won’t be able to shrink, ever. This allows us to avoid setting up the SIGBUS handlers on such file descriptors.
Signed-off-by: Emmanuel Gil Peyrot linkmauve@linkmauve.fr