The resulting firmware files should only contain the runtime path.
Fixes commit 26ce90fd ("Makefile: install the edk2 firmware images
and their descriptors")

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20190530192812.17637-1-olaf@aepfle.de>
Fixes: https://bugs.launchpad.net/qemu/+bug/1838703


Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>