Update the OPAL glue configure code to correctly link the opal/pmix4
component to the hwloc used by OMPI instead of defaulting to the
system-level hwloc. Required a corresponding update to the PMIx hwloc
configure code so we treat hwloc the same way we handle libevent in
embedded scenarios.
Signed-off-by: Ralph Castain <rhc@pmix.org>