The 64 bit cl.exe version 16.00.30319.01 crashes with an internal
compiler error on the current check (and thus deduces it isn't
supported, even if the actual usage in libavuil/x86/cpu.c works
fine), but by assigning the value from the intrinsic to a variable,
or returning it, it works fine.

This error is fixed in cl.exe version 16.00.40219.01.
Signed-off-by: Martin Storsjö <martin@martin.st>