The probe piped the candidate binary into grep to look for -B support.
mkimage with no arguments prints usage and exits non-zero, and this script
runs under `set -euo pipefail`, so the pipeline reported failure even when
grep matched. Every candidate was rejected and the script failed closed with
"no mkimage on PATH supports -B" while a capable mkimage 2025.01 sat first
on PATH, making it impossible to build a boot.img at all.
Neutralise the probed command's exit status before the pipe. Sentinel
comments now bracket the probe so the new regression test extracts and
exercises the shipping code rather than a copy of it.
Closes#17
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T2D2KtdgwbhbF6Mo64eUrn
