No need for buildtoc to scan ext/, now that it runs after the build process.

No need for buildtoc to scan ext/, now that it runs after the build process.

Since 7eb47696deb9a734, buildtoc has been run as part of the build process,
hence it has all modules copied to lib/ from ext/ (dist/ and cpan/), where
its scan finds them.

Previously it was run by the committers as and when (and sometimes not often
enough), and the generated pod/perltoc.pod checked in. Hence it might be run
on a clean checkout, and so couldn't assume that everything would be in lib/

This scan of lib/ is why buildtoc can still pick up all the modules, despite
their migration to cpan/ and dist/, which it has no idea about.

Also, scanning lib/ rather than ext/ means that Pod for modules that are not
being installed on this platform won't be included, which makes for a more
accurate perltoc.pod