use dontBuild instead of hacks

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

pkgs/applications/graphics/sane/backends/brscan4/default.nix

@@ -1,12 +1,6 @@
 { stdenv, fetchurl, callPackage, patchelf, makeWrapper, coreutils, libusb }:
 
-/*
-
-
-*/
-
 let
-
   myPatchElf = file: with stdenv.lib; ''
     patchelf --set-interpreter \
       ${stdenv.glibc}/lib/ld-linux${optionalString stdenv.is64bit "-x86-64"}.so.2 \
@@ -15,10 +9,7 @@ let
 
   udevRules = callPackage ./udev_rules_type1.nix {};
 
-in
-
-stdenv.mkDerivation rec {
-
+in stdenv.mkDerivation rec {
   name = "brscan4-0.4.3-3";
   src = fetchurl {
     url = "http://download.brother.com/welcome/dlf006645/${name}.amd64.deb";
@@ -32,8 +23,7 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ makeWrapper patchelf coreutils udevRules ];
   buildInputs = [ libusb ];
-  buildPhase = ":";
-
+  dontBuild = true;
 
   patchPhase = ''
     ${myPatchElf "opt/brother/scanner/brscan4/brsaneconfig4"}
@@ -47,7 +37,6 @@ stdenv.mkDerivation rec {
   '';
 
   installPhase = ''
-
     PATH_TO_BRSCAN4="opt/brother/scanner/brscan4"
     mkdir -p $out/$PATH_TO_BRSCAN4
     cp -rp $PATH_TO_BRSCAN4/* $out/$PATH_TO_BRSCAN4

pkgs/applications/graphics/sane/backends/brscan4/udev_rules_type1.nix

@@ -1,8 +1,6 @@
 { stdenv, fetchurl, libsaneUDevRuleNumber ? "49"}:
 
-
 stdenv.mkDerivation rec {
-
   name = "brother-udev-rule-type1-1.0.0-1";
 
   src = fetchurl {
@@ -10,7 +8,7 @@ stdenv.mkDerivation rec {
     sha256 = "0i0x5jw135pli4jl9mgnr5n2rrdvml57nw84yq2999r4frza53xi";
   };
 
-  buildInputs = [ ];
+  dontBuild = true;
 
   unpackPhase = ''
     ar x $src
@@ -37,9 +35,6 @@ stdenv.mkDerivation rec {
     sed -i -e s/SYSFS/ATTR/g opt/brother/scanner/udev-rules/type1/*.rules
   '';
 
-
-  buildPhase = ":";
-
   installPhase = ''
     mkdir -p $out/etc/udev/rules.d
     cp opt/brother/scanner/udev-rules/type1/NN-brother-mfp-type1.rules \
@@ -57,4 +52,4 @@ stdenv.mkDerivation rec {
     license = stdenv.lib.licenses.unfree;
     maintainers = with stdenv.lib.maintainers; [ jraygauthier ];
   };
-}
+}