osmo-bsc_mgcp: Add LIBOSMONETIF_{CFLAGS,LIBS}

The osmo-mgw gerrit build is currently failing with the following error:

make[3]: Entering directory '/build/src/osmo-bsc_mgcp'
  CC       mgcp_main.o
In file included from ../../include/osmocom/legacy_mgcp/mgcp_internal.h:146:0,
                 from mgcp_main.c:36:
../../include/osmocom/legacy_mgcp/osmux.h:4:33: fatal error: osmocom/netif/osmux.h: No such file or directory
 #include <osmocom/netif/osmux.h>
                                 ^
compilation terminated.

Let's make sure we're adding the required flags/libs for libosmonetif dependency

Related: OS#2829
Change-Id: I402314532590498a6340dc14101a32b605cd5e09
2 files changed