Adding module for selinux bug metadata feature

Concatenates all 'bug_map' files and places the file on device under
/system/etc/selinux/bug_mappings

Bug: 34997782
Test: the file appears properly on device when bug_map files are present
Change-Id: I12d6c90983932f7d5e1d1f7586fa30a5edd7b0c5