The SERVER-136184 backport on v9.0-staging (512f0436) requires release configurations to run on release-* distros, and the splunk custom builds' MONGO_VERSION_OVERRIDE makes every compile in the variant resolve public-release — so every compile outside the release-pool task groups has failed on plain rhel8.8-large since 2026-10-14 (tracked in BF-46787).

Fix: PR 64532 moves the standalone compile tasks (compile_mongor, crypt_create_lib, stitch_support_create_lib, stitch_support_install_and_run_tests) and the integration compile TG to the release pools; no task-set change — test tasks stay on the standard pools. Verified green by evergreen patch 3111 and a follow-up patch covering stitch_support_install_and_run_tests.

No backport needed: v9.0-staging is the only branch where the splunk custom build and the guard coexist (master and v8.3-staging lack the build; v8.0's splunk variant already runs entirely on release pools).