don't use qemu for x86 builds

pmbootstrap tries to set-up the qemu user mode emulation when we're not even crosscompiling.

(021778) [16:19:25] Verify the version reported by the apk.static binary (must match the package version 2.7.2-r0)
(021778) [16:19:25] % /tmp/martijn/pmbootstrap9scgdaciapk --version
apk-tools 2.7.2, compiled for x86_64.
(021778) [16:19:25] Calculate depends of packages ['qemu-user-static-repack', 'qemu-user-static-repack-binfmt'], arch: x86_64
(021778) [16:19:25] Calculate depends of packages ['qemu-user-static-repack', 'qemu-user-static-repack-binfmt'], arch: x86_64
(021778) [16:19:25] parsing: /home/martijn/.local/var/pmbootstrap/chroot_native/usr/share/qemu-user-binfmt.txt
(021778) [16:19:25] filtering by architecture: amd64
(021778) [16:19:25] ERROR: Could not find key amd64_mask in binfmt info file: /home/martijn/.local/var/pmbootstrap/chroot_native/usr/share/qemu-user-binfmt.txt

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information