More accurate error messages when setting target release after mupdate - #11018

control: job assigned to worker 01KZ9P5J5VG3WGE13NBBVJMAHQ [factory aws, i-0bb0dacdb2be21315] (queued for 1 m 1 s)
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task: starting task 0: "setup"
task: process exited: duration 4118 ms, exit code 0
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task: starting task 1: "rust-toolchain"
task: process exited: duration 18011 ms, exit code 0
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task: starting task 2: "authentication"
task: process exited: duration 16 ms, exit code 0
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task: starting task 3: "clone repository"
task: process exited: duration 12594 ms, exit code 0
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task: starting task 4: "build"
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|    Compiling tufaceous-artifact v0.2.0 (https://github.com/oxidecomputer/tufaceous?branch= [...]
|    Compiling serde_with v3.21.0
|    Compiling omicron-ledger v0.1.0 (/work/oxidecomputer/omicron/ledger)
|    Compiling api_identity v0.1.0 (/work/oxidecomputer/omicron/api_identity)
|    Compiling iddqd v0.4.2
|    Compiling regress v0.10.5
|    Compiling macaddr v1.0.1
|    Compiling humantime v2.3.0
|    Compiling rustls-webpki v0.103.13
|    Compiling tokio-rustls v0.26.4
|    Compiling rustls-platform-verifier v0.6.2
|    Compiling hyper-rustls v0.27.7
|    Compiling reqwest v0.13.2
|    Compiling progenitor-client v0.14.0
|    Compiling progenitor-extras v0.2.0
|    Compiling omicron-common v0.1.0 (/work/oxidecomputer/omicron/common)
|    Compiling test-project v0.1.0 (/tmp/test-project)
|     Finished `release` profile [optimized] target(s) in 1m 04s
task: process exited: duration 102292 ms, exit code 0
|W| found 0 output files