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

Change-Id: Idc480ef51d94dc8bc73f775065d8bef303945866
diff --git a/net/nfd/Portfile b/net/nfd/Portfile
index 18fe5f0..81390ec 100644
--- a/net/nfd/Portfile
+++ b/net/nfd/Portfile
@@ -13,6 +13,7 @@
 license             GPL3+
 version             0.3.0
 epoch               3
+revision            1
 
 categories          net
 platforms           darwin
@@ -47,6 +48,7 @@
 }
 
 configure.env-append    SPHINX_BUILD=${prefix}/bin/sphinx-build-2.7
+configure.env-append PKG_CONFIG_PATH=${prefix}/lib/pkgconfig
 configure.cxxflags-append -std=c++11
 configure.cmd           ./waf configure