mavlink: fix linking

- link to nuttx_apps if CONFIG_NET is defined for "netlib_get_ipv4netmask"
- link to tunes

Signed-off-by: Jukka Laitinen <jukkax@ssrc.tii.ae>

src/modules/mavlink/CMakeLists.txt

@@ -123,3 +123,7 @@ px4_add_unit_gtest(SRC MavlinkStatustextHandlerTest.cpp
 		-Wno-address-of-packed-member # TODO: fix in c_library_v2
 		LINKLIBS modules__mavlink
 	)
+
+if(CONFIG_NET AND "${PX4_PLATFORM}" MATCHES "nuttx")
+	target_link_libraries(modules__mavlink PRIVATE nuttx_apps) # netlib_get_ipv4netmask
+endif()