After a resource image has bind mounted directories to the /sysroot
tree, this new syntax makes it possible to then mount further directories
from /sysroot on top of the newly mounted tree.
The concept of an 'unsealed' RealmFS no longer exists so support for this has been
removed. The result is much less complex and easier to understand and maintain.
Can now choose location at which resource image is mounted with
mount_at() method. This method also returns a handle which can be
used to later unmount the image.
citadel-tool now installed with a hardlink for each binary tool and
dispatches on the exe path to the tool implementation. This makes
the build faster, uses less disk space, and makes it easier to
create new small tools.
