[archiso] Use different logic when archisodevice == cow_device

* Now bootmnt/img_dev is always a ro-mount,
  and cowspace is first ro-mount then rw-mount.

* Fix a "hidden" bug: at the time of test [[ -ef ]], if devices nodes
  are not ready, such test will fail then archisodevice will mounted ro and
  when cow_device is mounted to be rw it fails.
  (I recently suffered this on a machine with slow USB)

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

archiso/hooks/archiso

@@ -167,11 +167,7 @@ archiso_mount_handler() {
 
     _init_loop_dev
 
-    if [[ "${archisodevice}" -ef "${cow_device}" ]]; then
-        _mnt_dev "${archisodevice}" "/run/archiso/bootmnt"
-    else
     _mnt_dev "${archisodevice}" "/run/archiso/bootmnt" "-r"
-    fi
 
     if [[ ! -f "${aitab}" ]]; then
         echo "ERROR: '${aitab}' file does not exist."
@@ -203,7 +199,8 @@ archiso_mount_handler() {
     fi
 
     if [[ -n "${cow_device}" ]]; then
-        _mnt_dev "${cow_device}" "/run/archiso/cowspace"
+        _mnt_dev "${cow_device}" "/run/archiso/cowspace" "-r"
+        mount -o remount,rw "/run/archiso/cowspace"
     else
         msg ":: Mounting /run/archiso/cowspace (tmpfs) filesystem, size=${cowspace_size}..."
         mkdir -p /run/archiso/cowspace

archiso/hooks/archiso_loop_mnt

@@ -11,11 +11,7 @@ archiso_loop_mount_handler () {
     newroot="${1}"
 
     msg ":: Setup a loop device from ${img_loop} located at device ${img_dev}"
-    if [[ "${img_dev}" -ef "${cow_device}" ]]; then
-        _mnt_dev "${img_dev}" "/run/archiso/img_dev"
-    else
     _mnt_dev "${img_dev}" "/run/archiso/img_dev" "-r"
-    fi
 
     _dev_loop=$(losetup -f)
     if ! losetup "${_dev_loop}" "/run/archiso/img_dev/${img_loop}"; then

archiso/install/archiso

@@ -14,6 +14,9 @@ build ()
     add_file /lib/udev/rules.d/95-dm-notify.rules
     add_file /lib/initcpio/udev/11-dm-initramfs.rules /lib/udev/rules.d/11-dm-initramfs.rules
 
+    # Add an empty fstab to avoid mount warning when -o remount is used (this should go to install/base)
+    : > "$BUILDROOT/etc/fstab"
+
     SCRIPT="archiso"
 }