rEFInd
You can choose to install rEFInd instead of Grub. Tested on EXT4.
pacman -S refind
refind-install
Now we need to edit the /boot/refind_linux.conf and make it a writable partition.
Further study on my part is necessary.
The refind.conf file contains lots of settings.
More info on Arch Linux and on Refind.
