[3.14] GH-136895: Update JIT builds to use LLVM 21 (GH-140329)#146420

mcepl wants to merge 4 commits intopython:3.14python/cpython:3.14from

openSUSE-Python:3.14-llvm21-compatopenSUSE-Python/cpython:3.14-llvm21-compatCopy head branch name to clipboard