extract_files: Add extract2() function

New devices have more than one partition, and it's very
cumbersome to try to extract all the blobs for different
partitions from one directory. Adding multi-directory support
breaks the existing single directory method, so a new function
was born. Also, have native support for SAR system image mounts
so you can do some argument simplification in the device
extract-files.sh

Change-Id: I94925897690fc23816a28c9cdb34fb11e46635b8
1 file changed