net/mlx: fix rdma-core glue path with EAL plugins

net/mlx: fix rdma-core glue path with EAL plugins

Glue object files are looked up in RTE_EAL_PMD_PATH by default when set and
should be installed in this directory.

During startup, EAL attempts to load them automatically like other plug-ins
found there. While normally harmless, dlopen() fails when rdma-core is not
installed, EAL interprets this as a fatal error and terminates the
application.

This patch requests glue objects to be installed in a different directory
to prevent their automatic loading by EAL since they are PMD helpers, not
actual DPDK plug-ins.

Fixes: f6242d0655cd ("net/mlx: make rdma-core glue path configurable")
Cc: stable@dpdk.org
Reported-by: Timothy Redaelli <tredaelli@redhat.com>
Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Tested-by: Timothy Redaelli <tredaelli@redhat.com>