gnuradio: fix wrapper

gnuradio-with-packages was not running makeWrapper on any of the
symlinked executables because `find $out/bin -type f -executable`
does not resolve symlinks. I don't understand how the old code
ever worked on any system.

pkgs/applications/misc/gnuradio/wrapper.nix

···
-{ stdenv, gnuradio, makeWrapper, python
-, extraPackages ? [] }:
+{ stdenv, gnuradio, makeWrapper, python, extraPackages ? [] }:
 
-with stdenv.lib;
+with { inherit (stdenv.lib) appendToName makeSearchPath; };
 
 stdenv.mkDerivation {
   name = (appendToName "with-packages" gnuradio).name;
···
     mkdir -p $out/bin
     ln -s "${gnuradio}"/bin/* $out/bin/
 
-    for file in $(find $out/bin -type f -executable); do
-        wrapProgram "$file" \
-            --prefix PYTHONPATH : ${stdenv.lib.concatStringsSep ":"
-                                     (map (path: "$(toPythonPath ${path})") extraPackages)} \
-            --prefix GRC_BLOCKS_PATH : ${makeSearchPath "share/gnuradio/grc/blocks" extraPackages}
+    for file in $(find -L $out/bin -type f); do
+        if test -x "$(readlink -f "$file")"; then
+            wrapProgram "$file" \
+                --prefix PYTHONPATH : ${stdenv.lib.concatStringsSep ":"
+                                         (map (path: "$(toPythonPath ${path})") extraPackages)} \
+                --prefix GRC_BLOCKS_PATH : ${makeSearchPath "share/gnuradio/grc/blocks" extraPackages}
+        fi
     done
-
   '';
+
   inherit (gnuradio) meta;
 }