filemap: check if dest is written for every block

If lenght parameter is provided to sparse_copy call
it's mandatory to check if the output file is fully
written after reading unmapped block from input file.

If it's not done then sparse_copy can write more data
than specified length.

(From OE-Core rev: 289b1767182982dfb6912e64481150697ba93e4d)

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

scripts/lib/wic/filemap.py

@@ -563,6 +563,13 @@ def sparse_copy(src_fname, dst_fname, skip=0, seek=0,
             start = skip
 
         fmap._f_image.seek(start, os.SEEK_SET)
+
+        written += start - skip - written
+        if length and written >= length:
+            dst_file.seek(seek + length, os.SEEK_SET)
+            dst_file.close()
+            return
+
         dst_file.seek(seek + start - skip, os.SEEK_SET)
 
         chunk_size = 1024 * 1024