When linprocfs is mounted the mode set to /compat/linux/proc is set to 555
while the package said 755 meaning pkg will try to change it 755 and fail
preventing upgrade or installation of the package because linprocfs does not
support changing attributes.
Enforce it to 555 to prevent that situation
/compat/linux/dev/shm a plain directory instead of a link to /tmp so we
don't force users to mount tmpfs on /tmp. This also makes /dev/shm a
separate namespace from /tmp.
Add libffi, needed by glib2.
PR: 207769
