rockspec: use luarocks' builtin builder to install specl modules.
rockspec: use luarocks' builtin builder to install specl modules.

* specl-git-1.rockspec (build): Use builtin type, and list all
module and bin source files.

Signed-off-by: Gary V. Vaughan <f9023000f29773649f3850298becb9544b5fd6a9@gnu.org>

gvvaughan/specl