Fix ANO linking warning (#463)

Currently, when building an app that uses the Advanced Network Operator
(ANO), CMake throws some warnings:

```
CMake Warning at operators/advanced_network/CMakeLists.txt:87 (target_link_libraries):
  Target "<target>" requests linking to directory
  "/usr/lib/x86_64-linux-gnu".  Targets may link only to libraries.  CMake is
  dropping the item.
```

Like it says, there are directories being passed into
target_link_libraries with -L which is not supported.

Instead, let's use target_link_directories which is already being used
in the ANO CMakeLists.txt file to pass those DPDK and DOCA directories.

Signed-off-by: John Moon <john.moon@vts-i.com>

operators/advanced_network/CMakeLists.txt

@@ -83,8 +83,8 @@ target_compile_options(advanced_network_rx PUBLIC ${DPDK_CFLAGS})
 target_compile_options(advanced_network_tx PUBLIC ${DPDK_CFLAGS})
 
 target_link_libraries(advanced_network_common PUBLIC holoscan::core)
-target_link_libraries(advanced_network_common PUBLIC -L${DPDK_LIBRARY_DIRS} ${DPDK_LIBRARIES} ${DPDK_EXTRA_LIBS})
-target_link_libraries(advanced_network_common PUBLIC -L${DOCA_LIBRARY_DIRS} -ldoca_gpunetio libdoca_gpunetio_device.a -ldoca_common -ldoca_argp -ldoca_eth -ldoca_flow)
+target_link_directories(advanced_network_common PUBLIC ${DPDK_LIBRARY_DIRS} ${DOCA_LIBRARY_DIRS})
+target_link_libraries(advanced_network_common PUBLIC ${DPDK_LIBRARIES} ${DPDK_EXTRA_LIBS} -ldoca_gpunetio libdoca_gpunetio_device.a -ldoca_common -ldoca_argp -ldoca_eth -ldoca_flow)
 target_link_libraries(advanced_network_rx PUBLIC advanced_network_common)
 target_link_libraries(advanced_network_tx PUBLIC advanced_network_common)