Travis Mac: set PKG_CONFIG_PATH to use custom freetype installation

Somehow the freetype-config script needs this now to report our custom installation not the system one (which may not exist). I'm not sure why it worked before the dependecy update but maybe the builds scripts in FTGL fixed that for us in the past.

mac_build/buildFTGL.sh

@@ -66,6 +66,9 @@ while [[ $# -gt 0 ]]; do
     shift # past argument or value
 done
 
+# needed for ftgl 2.1.3-rc5 to find our freetype 2.9 build not the system one
+export PKG_CONFIG_PATH=${libftpath}/lib/pkgconfig:${PKG_CONFIG_PATH}
+
 SRCDIR=$PWD
 
 if [ "${doclean}" != "yes" ]; then