Switched to Perl local::lib for local compilation.

Taken from upstream Slic3r, thanks @alexrj.

t/fill.t

@@ -9,6 +9,7 @@ plan tests => 19;
 BEGIN {
     use FindBin;
     use lib "$FindBin::Bin/../lib";
+    use local::lib "$FindBin::Bin/../local-lib";
 }
 
 use List::Util qw(first sum);