Add Flatcar ARM64 support

roles/netbootxyz/templates/menu/flatcar.ipxe.j2

@@ -11,7 +11,10 @@ goto ${menu}
 
 :flatcar
 set os {{ releases.flatcar.name }}
-menu ${os}
+set os_arch ${arch}
+iseq ${os_arch} x86_64 && set os_arch amd64 ||
+iseq ${os_arch} arm64 && set os_arch arm64 ||
+menu ${os} - Current Arch [ ${os_arch} ]
 item --gap ${os}
 {% for item in releases.flatcar.versions %}
 item {{ item.code_name }} ${space} ${os} {{ item.name }}
@@ -27,7 +30,7 @@ goto flatcar_exit
 :alpha
 :edge
 set release ${menu}
-set base-url http://${release}.release.flatcar-linux.net/amd64-usr/current
+set base-url http://${release}.release.flatcar-linux.net/${os_arch}-usr/current
 kernel ${base-url}/flatcar_production_pxe.vmlinuz ${flatcar_firstboot} ${flatcar_params} flatcar.autologin=tty1 flatcar.autologin=ttyS0 initrd=flatcar_production_pxe_image.cpio.gz ${cmdline}
 initrd ${base-url}/flatcar_production_pxe_image.cpio.gz
 boot

roles/netbootxyz/templates/menu/linux-arm.ipxe.j2

@@ -11,6 +11,7 @@ item centos ${space} CentOS
 item debian ${space} Debian
 item fedora ${space} Fedora
 item coreos ${space} Fedora CoreOS
+item flatcar ${space} Flatcar Container Linux
 item gentoo ${space} Gentoo
 item kali ${space} Kali
 item nixos ${space} NixOS