examples/l3fwd-graph: fix pkg-config usage
examples/l3fwd-graph: fix pkg-config usage

This example missed the fixes from commit 69b1bb49ed82
("examples: hide error for missing pkg-config path flag") and
commit 12a652a02b08 ("examples: fix build with old pkg-config").

Fixes: 08bd1a174461 ("examples/l3fwd-graph: add graph-based l3fwd skeleton")
Cc: stable@dpdk.org

Signed-off-by: David Marchand <f28529695cfa9e3e1eb84e7072aa626af4abb18e@redhat.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk