T11758 testcase help needed

[Alex Dzyoba]

Hi, all!

I was working on #11758, which is about dropping binutils<2.17 hack, and while
it was relatively easy to remove the hack itself, I'm not sure how to add a
test case for it.

As I understand, after removing the aforementioned hack, native codegen now
shouldn't generate sign extension. So my question is how to test it? Should it
be Cmm file that will be tested with `compile_cmp_asm` like memcpy in
"codeGen/should_gen_asm/memcpy.cmm"? Or should I stick to
the Haskell test?

Thanks,
Alex Dzyoba