.homebrew-build-env: Add ntl dirs

Author: Matthias Koeppe

.homebrew-build-env

@@ -23,7 +23,7 @@ export PKG_CONFIG_PATH
 LIBRARY_PATH="$HOMEBREW/lib$LIBRARY_PATH"
 [ -z "$CPATH" ] || CPATH=":${CPATH}"
 CPATH="$HOMEBREW/include$CPATH"
-for l in readline bzip2; do
+for l in readline bzip2 ntl; do
     if [ -d "$HOMEBREW/opt/$l/lib" ]; then
         LIBRARY_PATH="$HOMEBREW/opt/$l/lib:$LIBRARY_PATH"
     fi