New release portability issue

[Damien Miller]

On Wed, 19 Feb 2025, Dennis Clarke via openssh-unix-dev wrote:

> 
>     On an old Fujitsu SPARC64 server running Solaris 10 there is no builtin
> compiler function for __builtin_popcount. This seems to be
> something new in libcrux_mlkem768_sha3.h header. There was no issue
> with openssh-9.8p1.
> 
>     The LLVM folks have neat little bit of code that can do the bit
> shifting and adding :
> 
> 
> https://github.com/llvm-mirror/compiler-rt/blob/master/lib/builtins/popcountdi2.c
> 
>     It would be better to use inline asm where the SPARC64 hardware does
> indeed have the popc instruction.

This is weird, because this code has not changed significantly since
9.8p1. It's possible that configure might be behaving differently,
could you try comparing the output of ./configure run on each
version?