with having them people can just specify where the clang stuff is
installed, if its not possible to find it in the default location.
This fixes a bug where clang was not found, dirs: is meant as exclusive
parameter, so if you specify there a custom directory, then only THIS
specific directory will be used for the search. This fixes also that bug
and only specifies that argument if a custom location is given.
Andy Williams
Marcel Hollerbach