use dontBuild instead of hacks

changes:
 * buildPhase = "true"
 * buildPhase = ":"

pkgs/data/fonts/bakoma-ttf/default.nix

@@ -2,14 +2,18 @@
 
 stdenv.mkDerivation {
   name = "bakoma-ttf";
-  
+
   src = fetchurl {
     url = http://tarballs.nixos.org/bakoma-ttf.tar.bz2;
     sha256 = "1j1y3cq6ys30m734axc0brdm2q9n2as4h32jws15r7w5fwr991km";
   };
-  
-  buildPhase = "true";
-  installPhase = "mkdir -p $out/share/fonts/truetype; cp ttf/*.ttf $out/share/fonts/truetype";
+
+  dontBuild = true;
+
+  installPhase = ''
+    mkdir -p $out/share/fonts/truetype
+    cp ttf/*.ttf $out/share/fonts/truetype
+  '';
 
   meta = {
     description = "TrueType versions of the Computer Modern and AMS TeX Fonts";