pc update

Change-Id: Ib52dabd84ca8042b3188cbedda9cd0d07ecf0359
diff --git a/libndn-cert.pc.in b/libndn-cert.pc.in
index e173aa8..d4221e4 100644
--- a/libndn-cert.pc.in
+++ b/libndn-cert.pc.in
@@ -6,4 +6,5 @@
 Description: ndncert library
 Version: @VERSION@
 Libs: -L${libdir} -lndn-cert
-Cflags: -I${includedir}
\ No newline at end of file
+Cflags: -I${includedir}
+Requires: libndn-cxx >= 0.7.1
\ No newline at end of file