Fix the build
    
    ... by dropping the downstream libtool sed hack for removing rpaths.
    This was causing the introspection scanner to pick up system libs
    ('libgnome-keyring.so.0: cannot open shared object file')
    instead of the ones within the build tree.
    
    Apparently the libtool in current libgnome-keyring tarball doesn't add any
    lib64 rpaths, so we should be fine without the libtool hack.