Fix test to find deps in new process
Fix test to find deps in new process

Allows tests to pass with `zef install HTTP::Server::Tiny`. Failures are due to the depenency on HTTP::Tinyish being fulfilled by a CompUnit::Repository::FileSystem (usually `-I path/to/lib` or from a `use lib '...'`) and not a CompUnit::Repository::Installation.
tokuhirom/p6-HTTP-Server-Tiny,tokuhirom/p6-HTTP-Server-Tiny