wic: use sparse_copy to copy partitions

Copied partition images into final partitioned image using
sparse_copy API. This method preserves sparseness of the
final image. It also makes wic much faster, as unmapped
blocks of the partition images are not copied.

[YOCTO #9099]

(From OE-Core rev: 7f21427aca5df81d8881027fd98f71b821cf31d7)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/utils/partitionedfs.py

@@ -22,6 +22,7 @@ import os
 from wic import msger
 from wic.utils.errors import ImageError
 from wic.utils.oe.misc import exec_cmd, exec_native_cmd
+from wic.filemap import sparse_copy
 
 # Overhead of the MBR partitioning scheme (just one sector)
 MBR_OVERHEAD = 1
@@ -343,10 +344,7 @@ class Image(object):
             source = part['source_file']
             if source:
                 # install source_file contents into a partition
-                cmd = "dd if=%s of=%s bs=%d seek=%d count=%d conv=notrunc" % \
-                      (source, image_file, self.sector_size,
-                       part['start'], part['size'])
-                exec_cmd(cmd)
+                sparse_copy(source, image_file, part['start'] * self.sector_size)
 
                 msger.debug("Installed %s in partition %d, sectors %d-%d, "
                             "size %d sectors" % \