ferm: Fix import-ferm error importing ferm wrapped script instead of perlFile (#310626)

Co-authored-by: Antoine 'Toinux' Lesieur <toinux@laptaupe.local>

pkgs/tools/networking/ferm/default.nix

@@ -11,6 +11,10 @@ in stdenv.mkDerivation rec {
     sha256 = "sha256-wA2RDVOU5pZ1YI617g9QTVz9pB6ZCi2akbqsbfk+P5I=";
   };
 
+  patches = [
+    ./import-ferm-wrapped.patch
+  ];
+
   # perl is used at build time to gather the ferm version.
   nativeBuildInputs = [ makeWrapper perl ];
   buildInputs = [ perl ];

pkgs/tools/networking/ferm/import-ferm-wrapped.patch

@@ -0,0 +1,14 @@
+--- old/src/import-ferm
++++ new/src/import-ferm
+@@ -42,9 +42,9 @@
+     # find the main "ferm" program
+     my $ferm;
+     if ($0 =~ /^(.*)\//) {
+-        $ferm = "$1/ferm";
++        $ferm = "$1/.ferm-wrapped";
+     } else {
+-        $ferm = 'ferm';
++        $ferm = '.ferm-wrapped';
+     }
+ 
+     # Perl 5.24 requires this prefix or else it will only look in @INC