"Libpkix provides a much more complete an modern parsing of
certificates, most importantly policy parsing and handling cross
certificate environments correctly. Both of these are needed for EV (the
primary driver of getting libpkix in). (It also includes such things a
on the fly fetching of intermediate certs."

I'm not sure whether we can build without it in the future, in the
immediate short term we won't use it, but the coming NSS changes I
believe will depend on it.

-- Mike