Build fails with GCC14

[ggardet]

Build fails with GCC14.
Error log:

[   12s] gcc -c -g -O2 -fPIC -fvisibility=hidden -fomit-frame-pointer -Wall mem.c
[   12s] mem.c: In function ‘vm_i_byte’:
[   12s] mem.c:581:12: error: implicit declaration of function ‘inb’; did you mean ‘ins’? [-Wimplicit-function-declaration]
[   12s]   581 |     return inb(addr);
[   12s]       |            ^~~
[   12s]       |            ins
[   12s] mem.c: In function ‘vm_i_word’:
[   12s] mem.c:619:10: error: implicit declaration of function ‘inw’; did you mean ‘ins’? [-Wimplicit-function-declaration]
[   12s]   619 |   return inw(addr);
[   12s]       |          ^~~
[   12s]       |          ins
[   12s] mem.c: In function ‘vm_i_dword’:
[   12s] mem.c:657:10: error: implicit declaration of function ‘inl’; did you mean ‘ins’? [-Wimplicit-function-declaration]
[   12s]   657 |   return inl(addr);
[   12s]       |          ^~~
[   12s]       |          ins
[   12s] mem.c: In function ‘vm_o_byte’:
[   12s] mem.c:676:5: error: implicit declaration of function ‘outb’; did you mean ‘outs’? [-Wimplicit-function-declaration]
[   12s]   676 |     outb(val, addr);
[   12s]       |     ^~~~
[   12s]       |     outs
[   12s] mem.c: In function ‘vm_o_word’:
[   12s] mem.c:711:3: error: implicit declaration of function ‘outw’; did you mean ‘outs’? [-Wimplicit-function-declaration]
[   12s]   711 |   outw(val, addr);
[   12s]       |   ^~~~
[   12s]       |   outs
[   12s] mem.c: In function ‘vm_o_dword’:
[   12s] mem.c:748:3: error: implicit declaration of function ‘outl’; did you mean ‘outs’? [-Wimplicit-function-declaration]
[   12s]   748 |   outl(val, addr);
[   12s]       |   ^~~~
[   12s]       |   outs
[   12s] make: *** [Makefile:30: mem.o] Error 1

Likely a matter of adding #include <sys/io.h>.

[ggardet]

<sys/io.h> is only available on x86, and libx86emu is not used on aarch64, ppc64, etc, only on x86 for firmware purpose.
So, we may just need to allow build on x86 only.

[ggardet]

@wfeldt WDYT?