flash: support optional boot_bin_immutable_url in targets.json

[Phanendra Yarra (phanendra-qc)]

Summary

PR qualcomm-linux/meta-qcom#3069 splits the boot binaries archive into a main zip and a companion immutable zip. The Yocto recipe deploys both into the same DEPLOYDIR; this PR mirrors that behaviour in the Ubuntu build pipeline.

Changes

flash/parse-boards-config.py

• Add boot_bin_immutable_url as an optional field (defaults to "") in the schema doc comment and the setdefault normalization block.

flash/download-boot-bins.sh

• Extract the download+extract logic into a reusable download_and_extract() helper (URL deduplication cache preserved).
• After the main archive is placed in bins_<board>/, if boot_bin_immutable_url is set the immutable archive is downloaded (also deduplicated) and its contents are merged into the same bins_<board>/ directory via cp -a — exactly mirroring what the Yocto recipe does.
• Targets without boot_bin_immutable_url are fully backward-compatible.

Dependency

Companion PR in qcom-distro-images: #138 — adds boot_bin_immutable_url and bumps versions in config/resolute/iot/targets.json.

[Bjordis Collaku (bjordiscollaku)]

Reviewed the parser and download changes, and tested the flow locally with the real main and immutable archives for all four targets. The contents are merged correctly, shared URLs are downloaded only once, and targets without boot_bin_immutable_url continue to work as before. The implementation looks good to me. Please fix the DCO sign-off before merging.

[Phanendra Yarra (phanendra-qc)]

Reviewed the parser and download changes, and tested the flow locally with the real main and immutable archives for all four targets. The contents are merged correctly, shared URLs are downloaded only once, and targets without boot_bin_immutable_url continue to work as before. The implementation looks good to me. Please fix the DCO sign-off before merging.

Thanks for review, addressed DCO & also added cleanup of extact* folder post bin_ created