If you want to use Android-x86 for full feature, it's recommended to install on hdd instead using Vbox or Another emulator. But the problem is grub. Most of linux distribution cannot detect automaticly Android-x86. Also on Archlinux, using os-prober still doesn't detect android-x86.
To add android-x86 into archlinux GRUB2 list, you can add manually on /etc/grub.d/40_custom
Before editing GRUB.. install android-x86 first with grub installed. Then restore archlinux grub. Login to archlinux, open Android-x86 partition, open grub, then open menu.lst You will see list like this:
Now try to add, see mark list (grey), add like this into 40_custom
After you add custom entry, then.
#grub-mkconfig -o /boot/grub/grub.cfg
Ok that's now you can boot into android x86 system.