hadrian: Move ghcBinDeps into ghcLibDeps

This completes a5227080, the ghc-usage.txt and ghci-usage.txt file are also used by the ghc library so need to make sure they are present in the libdir even if we are not going to build ghc-bin.

This also fixes things for cross compilers because the stage2 cross-compiler requires the ghc-usage.txt file, but we are using the stage2 lib folder but not building stage3:exe:ghc-bin so ghc-usage.txt was not being generated.