libyaml-cpp: Build a shared library

Also, use multiple outputs.

pkgs/development/libraries/libyaml-cpp/default.nix

@@ -11,8 +11,14 @@ stdenv.mkDerivation rec {
     sha256 = "0qr286q8mwbr4cxz0y0rf045zc071qh3cb804by6w1ydlqciih8a";
   };
 
+  outputs = [ "dev" "out" ];
+
   buildInputs = [ cmake boost ];
 
+  cmakeFlags = "-DBUILD_SHARED_LIBS=ON";
+
+  enableParallelBuilding = true;
+
   meta = with stdenv.lib; {
     inherit (src.meta) homepage;
     description = "A YAML parser and emitter for C++";