Avoid magic $cwd in module search path RT #130883
Avoid magic $cwd in module search path RT #130883

https://rt.perl.org/Ticket/Display.html?id=130883

Similar to the Perl dot-inc security issue, but limit to when PERL6LIB (or `use lib`) is set to an empty string:

$ echo 'package { say "all your base" }' > NativeCall.pm6
$ PERL6LIB="" perl6 -e 'use NativeCall;'
all your base


Note this PR has a LTA error when using `use lib ""`:

$ perl6 -e 'use lib "";'
===SORRY!===
Too few positionals passed to 'repository-for-spec'; expected 3 arguments but got 0
tbrowder/rakudo,salortiz/rakudo,raydiak/rakudo,tbrowder/rakudo,tony-o/rakudo,Gnouc/rakudo,Gnouc/rakudo,awwaiid/rakudo,nbrown/rakudo,raydiak/rakudo,nbrown/rakudo,nbrown/rakudo,usev6/rakudo,awwaiid/rakudo,tony-o/rakudo,MasterDuke17/rakudo,labster/rakudo,salortiz/rakudo,raydiak/rakudo,awwaiid/rakudo,jonathanstowe/rakudo,labster/rakudo,jonathanstowe/rakudo,awwaiid/rakudo,softmoth/rakudo,labster/rakudo,MasterDuke17/rakudo,sjn/rakudo,usev6/rakudo,Gnouc/rakudo,lucasbuchala/rakudo,nbrown/rakudo,salortiz/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,nbrown/rakudo,salortiz/rakudo,lucasbuchala/rakudo,tbrowder/rakudo,sjn/rakudo,lucasbuchala/rakudo,softmoth/rakudo,labster/rakudo,salortiz/rakudo,sjn/rakudo,jonathanstowe/rakudo,tony-o/rakudo,lucasbuchala/rakudo,lucasbuchala/rakudo,Gnouc/rakudo,jonathanstowe/rakudo,tony-o/rakudo,tbrowder/rakudo,salortiz/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,softmoth/rakudo,sjn/rakudo,tbrowder/rakudo,usev6/rakudo,labster/rakudo,raydiak/rakudo,MasterDuke17/rakudo,rakudo/rakudo,tony-o/rakudo,Gnouc/rakudo,nbrown/rakudo,MasterDuke17/rakudo,softmoth/rakudo,rakudo/rakudo,rakudo/rakudo,tony-o/rakudo,sjn/rakudo,usev6/rakudo,rakudo/rakudo,awwaiid/rakudo,softmoth/rakudo,labster/rakudo,jonathanstowe/rakudo,rakudo/rakudo,usev6/rakudo,rakudo/rakudo