OS X, Hivex: Use MacPorts libraries

This resolves a fresh issue with iconv and OS X's default build.

Thanks to Richard W.M. Jones for the solution.

(cherry picked from commit a5823f310000550ebd182128427d189ce82c208e)

Conflicts:
	deps/build_submodules.sh
	tests/for_throwaway_vms_only/build_on_osx-10.7.sh
	tests/for_throwaway_vms_only/build_on_osx-10.8.sh