[llvm] [SDag][ARM][RISCV] Allow lowering CTPOP into a libcall (PR #99752)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

@antmox Could you please take a look? I've already [reverted](https://github.com/llvm/llvm-project/pull/101673) the changes, but I'd like to reland them if they're not the reason of the failures.


https://github.com/llvm/llvm-project/pull/99752