emulators/qemu: fix build on powerpc64*

1. asm/cputable.h is Linux-only.
2. FreeBSD doesn't yet officially support POWER10, so we don't define PPC_FEATURE2_ARCH_3_1.

emulators/qemu/files/patch-util_cpuinfo-ppc.c

@@ -0,0 +1,18 @@
+--- util/cpuinfo-ppc.c.orig	2023-08-29 11:28:39 UTC
++++ util/cpuinfo-ppc.c
+@@ -9,8 +9,14 @@
+ #ifdef CONFIG_GETAUXVAL
+ # include <sys/auxv.h>
+ #else
+-# include <asm/cputable.h>
++# ifdef __linux__
++#  include <asm/cputable.h>
++# endif
+ # include "elf.h"
++#endif
++
++#ifndef PPC_FEATURE2_ARCH_3_1
++# define PPC_FEATURE2_ARCH_3_1       0x00040000
+ #endif
+ 
+ unsigned cpuinfo;