use dontBuild instead of hacks

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

pkgs/data/fonts/vista-fonts/default.nix

@@ -2,7 +2,7 @@
 
 stdenv.mkDerivation {
   name = "vista-fonts-1";
-  
+
   src = fetchurl {
     url = http://download.microsoft.com/download/f/5/a/f5a3df76-d856-4a61-a6bd-722f52a5be26/PowerPointViewer.exe;
     sha256 = "07vhjdw8iip7gxk6wvp4myhvbn9619g10j9qvpbzz4ihima57ry4";
@@ -10,14 +10,14 @@ stdenv.mkDerivation {
 
   buildInputs = [cabextract];
 
-  unpackPhase = "
+  unpackPhase = ''
     cabextract --lowercase --filter ppviewer.cab $src
     cabextract --lowercase --filter '*.TTF' ppviewer.cab
     sourceRoot=.
-  ";
-  
-  buildPhase = "true";
-  
+  '';
+
+  dontBuild = true;
+
   installPhase = ''
     mkdir -p $out/share/fonts/truetype
     cp *.ttf $out/share/fonts/truetype