Fix arch fstab

bash/install_arch.sh

@@ -117,6 +117,7 @@ EOF
 	mkdir /mnt/boot
 	mount ${DEVICE}1 /mnt/boot
 
+	mkdir /mnt/etc
 	cat <<EOT > /mnt/etc/fstab
 /dev/sda3 /     ext4 noatime,discard 0 1
 /dev/sda1 /boot vfat defaults        0 2
@@ -163,6 +164,7 @@ EOF
 
 	mount ${DEVICE}2 /mnt
 
+	mkdir /mnt/etc
 	cat <<EOT > /mnt/etc/fstab
 /dev/sda2 /     ext4 noatime,discard 0 1
 /dev/sda1 none  swap sw              0 0