Issue Summary

Older Evergreen branches (e.g., 8.3) are failing to compile the develop branch of WiredTiger because the toolchain file ../cmake/toolchains/mongodbtoolchain_stable_gcc.cmake has been removed from develop, resulting in build failures such as:

[2026/05/26 15:13:02.668]   Could not find toolchain file:
[2026/05/26 15:13:02.668]   ../cmake/toolchains/mongodbtoolchain_stable_gcc.cmake

Context

• The develop branch no longer contains the toolchain file due to recent changes (alexander.blekhman@mongodb.com reworked this).
• Evergreen tasks for older branches (e.g., 8.3) attempt to compile develop using their own evergreen.yml, which expects the toolchain file to exist.
• Compatibility testing requires compiling develop from older branches, but the current configuration is incompatible with the new develop branch setup.
• Example Evergreen task: Evergreen 8.3 compile failure
• The build baron is continuously failing due to this issue.

Proposed Solution

• Update the "configure wiredtiger" function in older branches so that it can configure a branch without toolchain files if CMakePresets.json is found.
• Suggested fix:

  if [[ "$(uname -s)" == "Linux" && -f CMakePresets.json ]]; then
    CMAKE_TOOLCHAIN_FILE="--preset linux-gcc"
  else
    CMAKE_TOOLCHAIN_FILE=-DCMAKE_TOOLCHAIN_FILE=../cmake/toolchains/mongodbtoolchain_stable_gcc.cmake
  fi
  

• Consider backporting the changes from develop or updating the build scripts to handle both cases.
• Remove or update the toolchain file reference in evergreen.yml for older branches as appropriate.

Original Slack thread: https://mongodb.slack.com/archives/C0520RCK0C9/p1779772863856469
This ticket was generated by AI from a Slack thread.