Hi Hinko!

Packaging is done in a sandboxed environment that is totally independent of your
installation.
So you don't need to install gcc at all.

You don't need to propagate the input either, because the end-user only cares
about the package, not the dependent libraries.

Last, you seem to have forgotten the version in the input.

Try with the following line instead:

    (inputs
      `(("gcc:lib" ,gcc-5 "lib")))

Hope that helps.



-- 
Pierre Neidhardt

Speak softly and own a big, mean Doberman.
		-- Dave Millman