Expand insertkeys.py script to allow union of files.

Allow script to union mac_permissions.xml files
specified using the BOARD_SEPOLICY_DIRS and
BOARD_SEPOLICY_UNION constructs.

Change-Id: I4fc65fd1ab4c612f25e966f030247e54a270b614
Signed-off-by: rpcraig <rpcraig@tycho.ncsc.mil>
3 files changed