Load camlibs/iolibs using a relative path
Fix libraries names/versions for compatibility with homebrew
Fix rpath in Gphoto2
Fix usb iolob

In gp_port_library_list, it calls gp_port_info_list_append passing
a "generic" port (empty name).  The function returns -1 when a
generic port is pushed to empty list and the caller interprets this
as an error condition.