release.sh: make sure GNU gzip is used

[starius]

Change Description

On macOS, the default BSD gzip produces different output than the GNU gzip used on Linux. To ensure reproducible builds, we need to enforce the use of GNU gzip.

This is similar to what we already do for GNU tar.

While working on reproducible builds for Loop, I encountered this gzip issue and fixed it there. This PR applies the same fix to LND.

Steps to Test

Clone my branch into a fresh Git repository to ensure the state is clean and tagged with v0.0.1-test. Build it and compare the resulting hashes against the ones listed below:

$ git clone https://github.com/starius/lnd -b release-gnu-gzip
$ cd lnd
$ SKIP_VERSION_CHECK=1 make release sys="linux-arm64" tag=v0.0.1-test
5ec1abf5d2aa150cce7432a432977a7db99fdf2077431e09600cabe25c16a040  lnd-linux-arm64-v0.0.1-test.tar.gz
501bb50d83a69c7be37e516cc532821196051263d1193aaed4ab6d9c16a349e7  lnd-linux-arm64-v0.0.1-test/lncli
add47fa88e47f997ad52df5c2edb3b00198a4d303105b17075b2b7d8fd96019d  lnd-linux-arm64-v0.0.1-test/lnd
913776165bdeff65ac941f101e4928ac004d39da78ce62c026c98b0d2e4ffb3c  lnd-source-v0.0.1-test.tar.gz
3a914dc298f1441a3432118b8674908def8e52f87092863d14a227e0f5f9d80d  vendor.tar.gz

If you are on macOS, this verification is especially valuable, since this PR fixes reproducibility issues caused by BSD gzip compression on macOS.

Pull Request Checklist

Testing

• Your PR passes all CI checks.
• Tests covering the positive and negative (error paths) are included.
• Bug fixes contain tests triggering the bug to prevent regressions.

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[gemini-code-assist]

Summary of Changes

Hello @starius, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request aims to enhance the reproducibility of LND's release builds by standardizing the gzip utility used during the packaging process. It specifically targets inconsistencies between macOS's default BSD gzip and the GNU gzip commonly found on Linux, ensuring that the compressed output is identical regardless of the build environment. This change is crucial for maintaining consistent build hashes and improving overall build reliability.

Highlights

• Reproducible Builds: Ensures that release builds are reproducible across different operating systems by enforcing the use of GNU gzip, similar to how GNU tar is already handled.
• macOS Compatibility: Addresses the issue where the default BSD gzip on macOS produces different output compared to GNU gzip on Linux, which can lead to non-reproducible build artifacts.
• Gzip Enforcement Logic: Adds logic to the release.sh script to check if the system's gzip is GNU. If not, it attempts to use ggzip (GNU gzip installed via Homebrew) and provides an error message with installation instructions if ggzip is not found.

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[gemini-code-assist]

Code Review

This pull request aims to ensure reproducible builds by enforcing the use of GNU gzip. The approach is sound and consistent with how GNU tar is handled. However, I found a critical issue where the new logic is not applied because the gzip command is still hardcoded in one place. My review includes a comment detailing the problem and how to fix it.

[lightninglabs-deploy]

@starius, remember to re-request review from reviewers when ready