ndnping, nfd, repo-ng: Make sure that PKG_CONFIG_PATH variable is properly set towards macports

Change-Id: Idc480ef51d94dc8bc73f775065d8bef303945866
diff --git a/net/repo-ng/Portfile b/net/repo-ng/Portfile
index 84c5df4..0cae2de 100644
--- a/net/repo-ng/Portfile
+++ b/net/repo-ng/Portfile
@@ -12,6 +12,7 @@
 homepage            https://github.com/named-data/repo-ng
 license             GPL-3+
 version             0.0.6
+revision            1
 
 categories          net
 platforms           darwin
@@ -31,6 +32,7 @@
 use_configure       yes
 
 configure.cxxflags-append -std=c++11
+configure.env-append PKG_CONFIG_PATH=${prefix}/lib/pkgconfig
 configure.cmd       ./waf configure
 
 build.cmd           ./waf