sbagen: Fix build

pkgs/applications/misc/sbagen/default.nix

···
 { stdenv, fetchurl }:
 
-stdenv.mkDerivation {
+stdenv.mkDerivation rec {
   name = "sbagen-1.4.4";
 
-  buildPhases = "buildPhase installPhase";
+  src = fetchurl {
+    url = "http://uazu.net/sbagen/${name}.tgz";
+    sha256 = "0w62yk1b0hq79kl0angma897yqa8p1ww0dwydf3zlwav333prkd2";
+  };
+
+  postPatch = ''
+    patchShebangs ./mk
+  '';
 
   buildPhase = "./mk";
 
···
     cp --target-directory=$out/share/sbagen/doc README.txt SBAGEN.txt theory{,2}.txt {wave,holosync,focus,TODO}.txt
   '';
 
-  src = fetchurl {
-    url = http://uazu.net/sbagen/sbagen-1.4.4.tgz;
-    sha256 = "0w62yk1b0hq79kl0angma897yqa8p1ww0dwydf3zlwav333prkd2";
-  };
-
-  meta = { 
+  meta = {
     description = "Binaural sound generator";
     homepage = http://uazu.net/sbagen;
     license = "GPL";
+    platforms = [ "i686-linux" ];
   };
 }