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

[via llvm-commits]

koachan wrote:

> Note that `__ctzdi2` has a similar workaround. Currently, it doesn't call itself recursively, but it will start doing so in the future, once we start promoting 32-bit `CTTZ_ZERO_UNDEF`.

Noted, will do another PR for it after this lands.

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