dpdk: Tell DPDK whether to build static or shared libraries

The DPDK build system ignores this, so it always builds both. But at
least if they were to fix it we'd be telling them the right thing.

Signed-off-by: Ben Walker <ben@nvidia.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/21387

 (master)

(cherry picked from commit 662f70fd)
Change-Id: I94d2a974aa6ad907f7f6d19f850741de35782c83
Signed-off-by: Marek Chomnicki <marek.chomnicki@intel.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/21599


Reviewed-by: Konrad Sztyber <konrad.sztyber@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>