Shrink the ISOs: no GPU drivers in the live initrd, server without GPU and sound firmware

- build-iso.sh patches the container's mklive copy: dracut omits amdgpu,
  radeon, nouveau, i915 and xe (and so their firmware) from the live initrd,
  mksquashfs uses 1 MB blocks with the x86 BCJ filter. initrd 245 -> 89 MB.
- das-server 0.2.0 ships /etc/xbps.d/das-server.conf that ignores
  linux-firmware-nvidia, sof-firmware and alsa-firmware; the server ISO
  passes the same list to mklive -g.
- das-install-common 0.2.0: postinstall drops mklive-ignore.conf.

Desktop ISO 1.96 -> 1.72 GB, server ISO 1.57 -> 1.14 GB.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

srcpkgs/das-install-common/files/postinstall

@@ -23,6 +23,9 @@ if ! grep -q '^[^#]*[[:space:]]/tmp[[:space:]]' /etc/fstab; then
 	echo "tmpfs /tmp tmpfs defaults,nosuid,nodev 0 0" >>/etc/fstab
 fi
 
+# mklive's list of packages left out of the image; das-server keeps its own
+rm -f /etc/xbps.d/mklive-ignore.conf
+
 # Guest tools only help inside their own hypervisor (VirtualBox's ones even
 # complain at every login elsewhere).
 machine=$(cat /sys/class/dmi/id/sys_vendor /sys/class/dmi/id/product_name 2>/dev/null || true)