Rewrite QEMU scripts #413

Job	Run time
live-iso (x86_64, flagship/flagship-live)	8m 22s
image (x86_64, base/base-disk)	17m 45s
live-iso (x86_64, gnome/gnome-live)	21m 34s
image (x86_64, flagship/base-disk)	8m 34s
live-iso (x86_64, plasma/plasma-live)	24m 14s
image (x86_64, gnome/base-disk)	2m 50s
live-iso (x86_64, xfce/xfce-live)	7m 36s
image (x86_64, plasma/base-disk)	35m 1s
live-iso (aarch64, flagship/flagship-live)	1s
image (x86_64, xfce/base-disk)	9m 42s
live-iso (aarch64, gnome/gnome-live)	1s
image (aarch64, base/base-disk)	11s
live-iso (aarch64, plasma/plasma-live)	1s
image (aarch64, flagship/base-disk)	10s
live-iso (aarch64, xfce/xfce-live)	1s
image (aarch64, gnome/base-disk)	11s
image (aarch64, plasma/base-disk)	1s
image (aarch64, xfce/base-disk)	1s
push-image	1s
	2h 16m 17s

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