openharmony: Support qemuarm-efi, qemuarm64-efi and raspberrypi4-64

Add support for qemuarm-efi, qemuarm64-efi and raspberrypi4-64 target
machines, and create some symlinks to work with Oniro's filesystem
layout (read-only / and writable partitions under /run/mount)

Signed-off-by: Bernhard Rosenkränzer <bernhard.rosenkraenzer.ext@huawei.com>