Only record a dependency once per precomp file
Only record a dependency once per precomp file

If more than one of our dependencies depend on the same dependency, we
recorded this base dependency more than once and also checked it more
than once when loading the precomp file. Filter out those duplicates as
early as possible instead.

Speeds up loading of complex module hierarchies, e.g. XML::LibXML:
Initial compile: 49s -> 34s
Changing a base module: 39s -> 19s
Loading unmodified: 3s -> 1.9s

usev6/rakudo,nbrown/rakudo,tbrowder/rakudo,usev6/rakudo,lucasbuchala/rakudo,nbrown/rakudo,nbrown/rakudo,jonathanstowe/rakudo,jonathanstowe/rakudo,jonathanstowe/rakudo,samcv/rakudo,salortiz/rakudo,tony-o/rakudo,rakudo/rakudo,tbrowder/rakudo,nbrown/rakudo,samcv/rakudo,raydiak/rakudo,Gnouc/rakudo,sjn/rakudo,salortiz/rakudo,samcv/rakudo,labster/rakudo,zostay/rakudo,raydiak/rakudo,awwaiid/rakudo,rakudo/rakudo,tony-o/rakudo,salortiz/rakudo,awwaiid/rakudo,labster/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,tony-o/rakudo,usev6/rakudo,tbrowder/rakudo,tbrowder/rakudo,rakudo/rakudo,raydiak/rakudo,labster/rakudo,zostay/rakudo,salortiz/rakudo,salortiz/rakudo,awwaiid/rakudo,nbrown/rakudo,jonathanstowe/rakudo,softmoth/rakudo,raydiak/rakudo,softmoth/rakudo,softmoth/rakudo,awwaiid/rakudo,rakudo/rakudo,Gnouc/rakudo,Gnouc/rakudo,tony-o/rakudo,sjn/rakudo,lucasbuchala/rakudo,tbrowder/rakudo,nbrown/rakudo,softmoth/rakudo,Gnouc/rakudo,zostay/rakudo,MasterDuke17/rakudo,sjn/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,softmoth/rakudo,zostay/rakudo,lucasbuchala/rakudo,samcv/rakudo,rakudo/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,sjn/rakudo,labster/rakudo,salortiz/rakudo,sjn/rakudo,awwaiid/rakudo,Gnouc/rakudo,lucasbuchala/rakudo,rakudo/rakudo,usev6/rakudo,labster/rakudo,jonathanstowe/rakudo,tony-o/rakudo,usev6/rakudo,labster/rakudo,lucasbuchala/rakudo,samcv/rakudo,MasterDuke17/rakudo,tony-o/rakudo