[QEMU] add support for qemux86 and qemux86-64
Add support for building Edgehog Things for x86 and x86-64 (QEMU's q35 machine) and base Poky BSP.
- separate qemuarm and qemux86 WKS templates (different wic partitioning)
- use cpio.gz as initramfs format instead of cpio.gz.u-boot for qemux86*
- set grub as bootloader (PREFERRED_PROVIDER_virtual/bootloader has to be set in edgehog-base.inc otherwise it's empty and the utility grub-editenv doesn't get installed)
- mount sda1 as /boot (needed by grub-editenv, therefore by rauc, to update the grub environment)
- install grub.conf (rauc configuration)
To run Edgehog Things, as opposed to Embedded, you can't use the built-in QEMU legacy BIOS, SeaBIOS. You can download OVMF (QEMU's UEFI bios) from here: https://www.kraxel.org/repos/jenkins/edk2/
Use ia32 for qemux86 and x64 for qemux86-64.
Use this command to run qemu:
BIOS=<path/to/OVMF.fd> runqemu [slirp] [nographic] [...]