Add support for "far dependencies"

AddVariationDependencies is used to add dependency modules that
have the same variations as the depending module, but with additional
variataions.  It cannot be used to add a dependency that is unrelated
to the depending module, for example a dependency on a code generator
that needs to run on the host to generate a target source file.

Add AddFarVariationDependencies, which adds a dependency on a module
that contains all the passed variations, but ignores the variations
of the depending module, as well as any unspecified variations on
the dependency module.

Change-Id: Ief696ec85cf33ad5fb187227d215c1c2e894f962