fatal error: 'cpuid.h' file not found

Trying "make -j8 buildworld" with a very recent tree (revision 366156).
This fails with

/usr/src/sys/contrib/openzfs/lib/libspl/include/sys/simd.h:34:10: fatal error: 'cpuid.h' file not found
#include <cpuid.h>

Could this be related to the flags I am using (in particular not
building CLANG)?

$ cat /etc/make.conf
MALLOC_PRODUCTION=yes
WITH_CCACHE_BUILD=yes
CCACHE_DIR=/usr/obj/ccache

$ cat /etc/src.conf
WITHOUT_CLANG=yes

$ cat /etc/src-env.conf
WITH_META_MODE=yes

I do kldload filemon before buildworld.

Trying minimize incremental build time and don't really care to build
clang every time. [I'd appreciate any advice on how to further cut down
the build time]

If it matters, I am using the cgit-beta tree.

Thanks!