1. [BUG] version_burn_in_gen fails: compile_variant enterprise-amazon2023-linux-x86-debug-tsan is undefined

1. 1. Summary

`version_burn_in_gen` fails on patches that touch tests scheduled on the
`enterprise-amazon2023-linux-x86-debug-tsan-all-feature-flags` variant, because that variant's
`compile_variant` expansion references `enterprise-amazon2023-linux-x86-debug-tsan` — a variant
that does not exist anywhere in the Evergreen project config.

1. 1. Failure

```
'generate.tasks' ('generate resmoke tasks config') in function 'generate version burn in' (step 12.9 of 12)
error translating project: variant selector contains unmatched criteria
enterprise-amazon2023-linux-x86-debug-tsan
```

1. 1. Repro

Submit any patch that modifies JS test files that are included in one of the task selectors on the
`enterprise-amazon2023-linux-x86-debug-tsan-all-feature-flags` variant (e.g. tests tagged
`.development_critical`, `.release_critical`, `.default`, or `.mongot_e2e_tests`).
`version_burn_in_gen` will attempt to generate burn-in tasks referencing the compile variant and
fail.

Example patch: SERVER-121972 (patch `6a1065de56430900070f17cf`) touches several
`jstests/extensions/` and `jstests/sharding/` files, triggering the failure.

1. 1. Root Cause

`etc/evergreen_yml_components/variants/sanitizer/test_dev.yml`, line 479:

```yaml

• name: enterprise-amazon2023-linux-x86-debug-tsan-all-feature-flags
  ...
  expansions:
  compile_variant: enterprise-amazon2023-linux-x86-debug-tsan# <-- does not exist
  ```

The variant `enterprise-amazon2023-linux-x86-debug-tsan` (without the `-all-feature-flags` suffix)
is not defined in any Evergreen config file in the repo. It was likely removed or renamed (possibly
as part of SERVER-122902, which migrated the TSAN variant to arm64) but the reference in
`test_dev.yml` was not updated.

1. 1. Why It Doesn't Surface on Master

On the master waterfall, `version_burn_in_gen` generates burn-in tasks for tests changed in each
individual commit. Most commits on master don't touch tests scheduled on this variant, so the broken
`compile_variant` reference is never exercised. Feature branch patches that modify many test files
are more likely to trigger it.

1. 1. Fix

Either:

*Option A (preferred):* Define the missing `enterprise-amazon2023-linux-x86-debug-tsan` compile
variant in the appropriate Evergreen config file (likely under
`etc/evergreen_yml_components/variants/sanitizer/`), if the intent is to cross-compile for x86
TSAN and run the test variant separately.

*Option B:* Update `compile_variant` in `test_dev.yml:479` to point to an existing variant that
produces the correct x86 TSAN binary (or remove the `compile_variant` override entirely if the
variant should compile its own binary).

1. 1. Affected File

`etc/evergreen_yml_components/variants/sanitizer/test_dev.yml` — line 469 (variant definition),
line 479 (`compile_variant` expansion)

1. 1. Labels / Components

• Component: Evergreen / CI Config
• Type: Bug
• Affects: version_burn_in_gen, patches touching extensions/sharding tests