jam: add yacc as build input

I am not sure why do I need this locally, it seems to be passing in hydra
anyway...

pkgs/development/tools/build-managers/jam/default.nix

@@ -1,4 +1,4 @@
-{stdenv, fetchurl}:
+{stdenv, fetchurl, yacc}:
 
 let
   bindir = if stdenv.system == "i686-linux" then "bin.linuxx86"
@@ -13,6 +13,8 @@ stdenv.mkDerivation {
     sha256 = "04c6khd7gdkqkvx4h3nbz99lyz7waid4fd221hq5chcygyx1sj3i";
   };
 
+  buildInputs = [ yacc ];
+
   installPhase = ''
     mkdir -p $out/bin
     cp ${bindir}/jam $out/bin