Add aarch64 support, WIP

Signed-off-by: Carsten Munk <carsten.munk@jollamobile.com>
Change default dev rules to make /dev/shm writable.

Also, stat functions on /dev/shm itself use original path
to create an illusion that emulated /dev/shm is tmpfs.
This is needed for sem_open() function from pthreads.

Signed-off-by: Oleg Girko <oleg.girko@jolla.com>
Merge pull request #4 from OlegGirko/master

Two changes necessary to build Mer for aarch64.