For Hugs, nhc98 and other compilers we do not know what packages are
already installed, so we just make some up, pretend that they do exist
and just hope for the best. We make them up based on what other package
the package we're currently building happens to depend on.
See inventBogusPackageId. Let's hope they really are installed... :-)
One could see this as all rather redundant - carefully making up bogus
information to satisfy a careful check. I prefer to see it as making
explicit something that was previously implicit. The proper solution is
to discover what packages are currently installed.