libtirpc: fix cross compilation

KRB5_CONFIG needs to be aviailable to get the right one when cross
compiling. These things should just use pkgconfig, but it’s fairly
easy to hack around this. krb5-config will not be on path because we
don’t know ahead of time what architecture it will be for.

pkgs/development/libraries/ti-rpc/default.nix

@@ -18,6 +18,7 @@ stdenv.mkDerivation rec {
                 '#if defined __APPLE_CC__ || defined __FreeBSD__ || !defined __GLIBC__'
   '';
 
+  KRB5_CONFIG = "${libkrb5.dev}/bin/krb5-config";
   nativeBuildInputs = [ autoreconfHook ];
   propagatedBuildInputs = [ libkrb5 ];