mscgen: add pkg-config build-time dependency

Signed-off-by: Sirio Balmelli <sirio@b-ad.ch>

pkgs/tools/graphics/mscgen/default.nix

@@ -1,4 +1,16 @@
-{ stdenv, fetchurl, flex, bison, gd, libpng, libjpeg, freetype, zlib, libwebp, runtimeShell }:
+{ stdenv
+, bison
+, fetchurl
+, flex
+, freetype
+, gd
+, libjpeg
+, libpng
+, libwebp
+, pkg-config
+, runtimeShell
+, zlib
+}:
 
 let
   version = "0.20";
@@ -12,7 +24,7 @@ stdenv.mkDerivation {
     sha256 = "3c3481ae0599e1c2d30b7ed54ab45249127533ab2f20e768a0ae58d8551ddc23";
   };
 
-  buildInputs = [ flex bison gd libjpeg libpng freetype zlib libwebp ];
+  buildInputs = [ bison flex freetype gd libjpeg libpng libwebp pkg-config zlib ];
 
   doCheck = true;
   preCheck = ''