use dontBuild instead of hacks

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

pkgs/applications/version-management/git-and-tools/svn2git/default.nix

@@ -13,22 +13,21 @@ stdenv.mkDerivation {
 
   buildInputs = [ ruby makeWrapper ];
 
-  buildPhase = "true";
+  dontBuild = true;
 
-  installPhase =
-    ''
-      mkdir -p $out
-      cp -r lib $out/
+  installPhase = ''
+    mkdir -p $out
+    cp -r lib $out/
 
-      mkdir -p $out/bin
-      substituteInPlace bin/svn2git --replace '/usr/bin/env ruby' ${ruby}/bin/ruby
-      cp bin/svn2git $out/bin/
-      chmod +x $out/bin/svn2git
+    mkdir -p $out/bin
+    substituteInPlace bin/svn2git --replace '/usr/bin/env ruby' ${ruby}/bin/ruby
+    cp bin/svn2git $out/bin/
+    chmod +x $out/bin/svn2git
 
-      wrapProgram $out/bin/svn2git \
-        --set RUBYLIB $out/lib \
-        --prefix PATH : ${git}/bin
-    '';
+    wrapProgram $out/bin/svn2git \
+      --set RUBYLIB $out/lib \
+      --prefix PATH : ${git}/bin
+  '';
 
   meta = {
     homepage = https://github.com/nirvdrum/svn2git;