flex, flex_2_6_1: fix tests

pkgs/development/tools/parsing/flex/2.6.1.nix

@@ -8,6 +8,12 @@ stdenv.mkDerivation rec {
     sha256 = "0fy14c35yz2m1n1m4f02by3501fn0cca37zn7jp8lpp4b3kgjhrw";
   };
 
+  postPatch = ''
+    patchShebangs tests
+  '' + stdenv.lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) ''
+    substituteInPlace Makefile.in --replace "tests" " ";
+  '';
+
   buildInputs = [ bison ];
 
   propagatedBuildInputs = [ m4 ];
@@ -21,11 +27,6 @@ stdenv.mkDerivation rec {
     sed -i Makefile -e 's/-no-undefined//;'
   '';
 
-  # disable tests which can't run on build machine
-  postPatch = stdenv.lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) ''
-    substituteInPlace Makefile.in --replace "tests" " ";
-  '';
-
   meta = {
     homepage = https://github.com/westes/flex;
     description = "A fast lexical analyser generator";