feat: enable signed images #500

Job	Run time
Get CoreOS versions	3s
Get Build Info	1s
Build CoreOS (fedora-coreos, stable, -nvidia, -zfs, pr-109-)	2m 51s
Build uCore (ucore, stable, -nvidia, -zfs, pr-109-)	3m 49s
Build CoreOS (fedora-coreos, stable, -nvidia, pr-109-)	2m 32s
Build uCore (ucore, stable, -nvidia, pr-109-)	3m 13s
Build CoreOS (fedora-coreos, stable, -zfs, pr-109-)	1m 38s
Build uCore (ucore, stable, -zfs, pr-109-)	2m 30s
Build CoreOS (fedora-coreos, testing, -nvidia, -zfs, pr-109-)	3m 3s
Build uCore (ucore, stable, pr-109-)	2m 43s
Build CoreOS (fedora-coreos, testing, -nvidia, pr-109-)	3m 5s
Build uCore (ucore, testing, -nvidia, -zfs, pr-109-)	4m 11s
Build CoreOS (fedora-coreos, testing, -zfs, pr-109-)	2m 10s
Build uCore (ucore, testing, -nvidia, pr-109-)	3m 26s
Build uCore (ucore, testing, -zfs, pr-109-)	2m 33s
Build uCore (ucore, testing, pr-109-)	2m 12s
Build HCI (ucore, stable, -nvidia, -zfs, pr-109-)	2m 59s
Build HCI (ucore, stable, -nvidia, pr-109-)	2m 59s
Build HCI (ucore, stable, -zfs, pr-109-)	3m 6s
Build HCI (ucore, stable, pr-109-)	2m 55s
Build HCI (ucore, testing, -nvidia, -zfs, pr-109-)	2m 30s
Build HCI (ucore, testing, -nvidia, pr-109-)	3m 33s
Build HCI (ucore, testing, -zfs, pr-109-)	4m 48s
Build HCI (ucore, testing, pr-109-)	3m 1s
Check all builds successful	1s
	1h 5m 52s

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