In #1520 it is described that FreeBSD doesn't detect symbolic links. The
same is true for OpenBSD. This diff fixes this issue for OpenBSD. I'm
guessing that something similar works for FreeBSD as well. However, I'm
unable to test this.
Similar to Apple, use the native physical core count sysctl, when available.
This is a little repetitive (it's basically the __APPLE__ method plus the
otherBSD method concatenated together) but seemed clearer than any way that
would totally eliminate repetition.
The __FreeBSD_version check only tests the version of the FreeBSD kernel
that zstd is compiled on; importantly, it may be run on a different version.
So the compile-time check is a little naive and needs to be able to fallback
to work on older versions of FreeBSD. For a similar reason, it may make
sense to simply eliminate the __FreeBSD_version check entirely. The
tradeoff is that a spurious sysctlbyname would be issued when -T0 is used on
older kernels.