Merge pull request #954 from mkroening/ci-cache #1815

Job	Run time
Check	1m 20s
Check docs	37s
Build	2m 6s
Clippy	2m 0s
Format	23s
Test	1m 45s
Run Hermit for Rust (x86_64 + kvm)	5m 34s
Run (x86_64, rusty_demo, none, dev)	5m 5s
Run (x86_64, rusty_demo, none, release)	4m 7s
Run (x86_64, httpd, virtio-net-pci, dev)	3m 4s
Run (x86_64, httpd, virtio-net-pci, release)	3m 56s
Run (x86_64, httpd, rtl8139, dev)	3m 12s
Run (x86_64, httpd, rtl8139, release)	3m 39s
Run (x86_64, testudp, virtio-net-pci, dev)	3m 48s
Run (x86_64, testudp, virtio-net-pci, release)	3m 52s
Run (x86_64, testudp, rtl8139, dev)	3m 12s
Run (x86_64, testudp, rtl8139, release)	3m 21s
Run (x86_64, hello_world, none, dev)	2m 48s
Run (x86_64, hello_world, none, release)	3m 22s
Run (aarch64, rusty_demo, none, dev)	5m 12s
Run (aarch64, rusty_demo, none, release)	3m 21s
Run (aarch64, httpd, virtio-net-pci, dev)	3m 13s
Run (aarch64, httpd, virtio-net-pci, release)	3m 44s
Run (aarch64, testudp, virtio-net-pci, dev)	3m 58s
Run (aarch64, testudp, virtio-net-pci, release)	3m 17s
	1h 19m 56s

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