Depend on libosmocore

Change-Id: If345c89293fcd7d1ad4f17214eea339951f25a5d
diff --git a/configure.ac b/configure.ac
index 5c034e5..cba4a0c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -73,6 +73,8 @@
 AC_HEADER_TIME
 AC_C_BIGENDIAN
 
+PKG_CHECK_MODULES(LIBOSMOCORE, libosmocore >= 0.10.0)
+
 AC_ARG_WITH(usrp1, [
     AS_HELP_STRING([--with-usrp1],
         [enable USRP1 gnuradio based transceiver])