MINOR: [Dev][Release] Stop post-04-website.sh script if archery isn't available

[amoeba]

Rationale for this change

The release script at dev/release/post-04-website.sh doesn't quite work right if archery isn't available. The PR gets made but the changelog isn't included. See when this happened during the 18.0.0 release: apache/arrow-site#551 (comment).

What changes are included in this PR?

Before the script does anything meaningful, it checks for archery and stops if it's not available.

Are these changes tested?

Yes.

Are there any user-facing changes?

No.

[amoeba]

Thanks @kou. I pulled your latest suggestions, tested locally, and it's working fine.

[kou]

+1

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 3 benchmarking runs that have been run so far on merge-commit 050fb80.

There were 132 benchmark results with an error:

• Commit Run on arm64-t4g-2xlarge-linux at 2024-11-25 05:19:41Z
  • tpch (R) with engine=arrow, format=parquet, language=R, memory_map=False, query_id=TPCH-07, scale_factor=1
  • tpch (R) with engine=arrow, format=native, language=R, memory_map=False, query_id=TPCH-09, scale_factor=1
• and 130 more (see the report linked below)

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 1 possible false positive for unstable benchmarks that are known to sometimes produce them.