sstatesig: Only apply group/other permissions to pseudo files

We hardlink some files into the build, such as licence files in
do_populate_lic tasks. Depending on the umask that the source tree
was checked out with, the group permissions would vary. This
results in inconsistent task outhashes.

Avoid this by ignoring the group/other bits unless we're under
pseudo context.

Bump the ABI numbers to ensure we don't see cache corruption from
earlier builds.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>