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

[via llvm-commits]

koachan wrote:

Pinging @wzssyqa and @topperc too since it appears that MIPS and RISC-V also use this check, just to make sure that this PR won't break things there.

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