wic/engine: fix copying directories into wic image with ext* partition

wic/engine: fix copying directories into wic image with ext* partition

wic uses debugfs to write on ext* partitions, but debugfs can only
write to the current working directory and it cannot copy complete
directory trees. Running 'wic ls' on a copied directory show this:
    -l: Ext2 inode is not a directory

Fix this by creating a command list for debugfs (-f parameter) when
recursive parsing the host directory in order to create a similar
directory structure (mkdir) and copy files (write) on each level
into the destination directory from the wic's ext* partition.

Signed-off-by: Daniel Dragomir <daniel.dragomir@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>