bin/image-writer: Add ext4 as a deployable image type

This is particularly problematic since qemu images switched to ext4 by
default and now cannot work properly with UIs like hob.

This patch adds in ext4 to the appropriate variable fixing this.

[YOCTO #7426]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bin/image-writer

@@ -34,7 +34,7 @@ from bb.ui.crumbs.hig.deployimagedialog import DeployImageDialog
 from bb.ui.crumbs.hig.imageselectiondialog import ImageSelectionDialog
 
 # I put all the fs bitbake supported here. Need more test.
-DEPLOYABLE_IMAGE_TYPES = ["jffs2", "cramfs", "ext2", "ext3", "btrfs", "squashfs", "ubi", "vmdk"]
+DEPLOYABLE_IMAGE_TYPES = ["jffs2", "cramfs", "ext2", "ext3", "ext4", "btrfs", "squashfs", "ubi", "vmdk"]
 Title = "USB Image Writer"
 
 class DeployWindow(gtk.Window):