FindLua: Search for all library names in each path
Add the `NAMES_PER_DIR` option to our `find_library` call so that all
names are considered in each path as we proceed through the search.
This allows locally-built unversioned libraries to be found before
versioned system libraries if they appear earlier in the set of paths to
be searched.
Suggested-by: Alan W. Irwin <[email protected]>
Brad King