Issue Summary

The Checkie Size project and related PRs are encountering s_all errors due to clang-format modifying files unexpectedly. This issue appears after the removal of explicit version pinning for clang-format, leading to discrepancies between toolchain versions used in CI and those expected by the project.

Context

• s_all errors are observed in Checkie Size and during merges (e.g., WT-17744, WT-17835).
• Example error output:

  Modifying examples/c/ex_file_system.c
  Modifying examples/c/ex_encrypt.c
  Modifying test/utility/test_util.h
  Modifying test/packing/intpack-test3.c
  Modifying src/checksum/power8/vec_crc32.c
  

• The project previously pinned clang-format version (see commit), but this was removed.
• Current toolchain version on host: MongoDB clang-format version 22.1.0
• PRs may specify older versions, e.g., Use clang-format 19.1.7, causing mismatch.
• This mismatch can cause s_all to fail or modify files unexpectedly.
• Discussion suggests that any binary change under the hood can now cause s_all to trip.

Proposed Solution

• Reinstate version pinning for clang-format in s_all, ensuring it checks for and transparently downloads the correct version if needed.
• Pin to MongoDB's toolchain version as intended, to match CI and developer environments.
• Update documentation and CI scripts accordingly.

Original Slack thread: https://mongodb.slack.com/archives/CUDFJEN8J/p1781565846013649
This ticket was generated by AI from a Slack thread.