standalone: add simple instance attestation server - #1076

control: job assigned to worker 01KKB1D0VBRB24B44JTZ6WFF2Y [factory aws, i-0765eb693b12b3c1d] (queued for 56 s)
...
task: starting task 0: "setup"
task: process exited: duration 4168 ms, exit code 0
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task: starting task 1: "rust-toolchain"
task: process exited: duration 31385 ms, exit code 0
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task: starting task 2: "authentication"
task: process exited: duration 23 ms, exit code 0
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task: starting task 3: "clone repository"
task: process exited: duration 1771 ms, exit code 0
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task: starting task 4: "build"
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| + pfexec mkdir -p /out
| + pfexec chown 12345 /out
| + cp .github/buildomat/phd-run-with-args.sh /out/phd-run-with-args.sh
| + mv target/debug/propolis-server-debug.tar.gz /out/propolis-server-debug.tar.gz
| + mv target/debug/phd-runner.tar.gz /out/phd-runner.tar.gz
| + cd /out
| + digest -a sha256 propolis-server-debug.tar.gz
| + digest -a sha256 phd-runner.tar.gz
task: process exited: duration 665341 ms, exit code 0
|W| found 5 output files
|W| uploading: /out/phd-run-with-args.sh (2573 bytes)
|W| uploaded: /out/phd-run-with-args.sh
|W| uploading: /out/phd-runner.sha256.txt (65 bytes)
|W| uploaded: /out/phd-runner.sha256.txt
|W| uploading: /out/phd-runner.tar.gz (116250963 bytes)
|W| uploaded: /out/phd-runner.tar.gz
|W| uploading: /out/propolis-server-debug.sha256.txt (65 bytes)
|W| uploaded: /out/propolis-server-debug.sha256.txt
|W| uploading: /out/propolis-server-debug.tar.gz (181270055 bytes)
|W| uploaded: /out/propolis-server-debug.tar.gz