[compiler-rt] [compiler-rt] Make sure __clzdi2 doesn't call itself recursively on sparc64 (PR #136737)

[via llvm-commits]

koachan wrote:

@wzssyqa & @topperc ping? Just want to make sure that this doesn't break MIPS and RISC-V

https://github.com/llvm/llvm-project/pull/136737