There's a merged pull request on the void-packages repository

nauty: disable native code (illegal instructions)
https://github.com/void-linux/void-packages/pull/35367

Description:
The package currently shipped in void gives me illegal instructions in a
nehalem cpu.

This commit fixes the issue by disabling native compilation unless a build
option is given; also disable popcnt which, although available on nehalem, is
not available in baseline x86_64.

An easy way to spot the issue is to run something like:
```
$ geng 2
>A geng -d0D1 n=2 e=0-1
Illegal instruction
```

#### Testing the changes
- I tested the changes in this PR: **YES**

I compiled with `./xbps-src build nauty` on a cascade lake cpu, then run `./xbps-src check nauty` on a nehalem cpu. This breaks before the present PR, and works ok after.

I also tested sagemath: previously I was getting a lot of doctest failures which are now fixed.

Cc: @leahneukirchen please merge this before sagemath.