mailutils: fix for sendmail path

pkgs/tools/networking/mailutils/default.nix

@@ -1,5 +1,5 @@
 { fetchurl, stdenv, gettext, gdbm, libtool, pam, readline
-, ncurses, gnutls, mysql, guile, texinfo, gnum4, dejagnu }:
+, ncurses, gnutls, mysql, guile, texinfo, gnum4, dejagnu, sendmailPath ? "/var/setuid-wrappers/sendmail" }:
 
 /* TODO: Add GNU SASL, GNU GSSAPI, and FreeBidi.  */
 
@@ -13,6 +13,8 @@ stdenv.mkDerivation rec {
 
   patches = [ ./path-to-cat.patch ./no-gets.patch ];
 
+  configureFlags = "--with-path-sendmail=${sendmailPath}";
+
   buildInputs =
    [ gettext gdbm libtool pam readline ncurses
      gnutls mysql guile texinfo gnum4 ]