gnuradio: also use PYTHONPATH from runtime environment

So that extra modules can be used without rebuilding (e.g. in
gnuradio-companion). PYTHONPATH from the environment is added *after*
the default deps.

pkgs/applications/misc/gnuradio/default.nix

@@ -53,7 +53,7 @@ stdenv.mkDerivation rec {
 
     for file in "$out"/bin/* "$out"/share/gnuradio/examples/*/*.py; do
         wrapProgram "$file" \
-            --set PYTHONPATH $PYTHONPATH:$(toPythonPath "$out") \
+            --prefix PYTHONPATH : $PYTHONPATH:$(toPythonPath "$out") \
             --set MATPLOTLIBRC "$out/share/gnuradio"
     done
   '';