Fix for OS X clang build error about rubichess

[Matthies]

Hmm. The include should already be there, at least for systems that support avx2.
Can you write something about your system and give the complete output of your "make" containing the error message? There should be some information about which CPU features are detected on your system.

[Matthies]

I see a problem now compiling with ARCH=x86-64-modern:
Undeclared identifier _tzcnt_u64 and _blsr_u64.

[tillchess]

The above fix should do it

[Matthies]

Maybe. But it is the wrong solution IMO. Hope to find a better one.

[tillchess]

My makefile output:

Compiler: clang
Arch: native
CPU features:

avx512: no
bmi2 : no
avx2 : no
bmi1 : no
lzcnt : no
popcnt: yes
ssse3 : yes
sse2 : yes
neon : no

ssse3 and sse2 & clang still needs the above fix.

[Matthies]

Okay, this seems a little different from mine. Can you give me the exact error message(s) you get when compiling?

[Matthies]

Latest master should compile now in Mac OS. Would be nice if you can confirm.

[tillchess]

Geht!

[Matthies]

Na denn mach ich hier mal zu :-)