gnuradio: Resolve darwin c++11 issues

-std=c++11 causes errors with OBJ-C files on Darwin. Inject dynamic compiler flag into every cmake file to work around this.

pkgs/applications/misc/gnuradio/default.nix

@@ -67,9 +67,10 @@ stdenv.mkDerivation rec {
 
   # patch wxgui and pygtk check due to python importerror in a headless environment
   preConfigure = ''
-    export NIX_CFLAGS_COMPILE="$NIX_CFLAGS_COMPILE -Wno-unused-variable -std=c++11"
+    export NIX_CFLAGS_COMPILE="$NIX_CFLAGS_COMPILE -Wno-unused-variable ${stdenv.lib.optionalString (!stdenv.isDarwin) "-std=c++11"}"
     sed -i 's/.*wx\.version.*/set(WX_FOUND TRUE)/g' gr-wxgui/CMakeLists.txt
     sed -i 's/.*pygtk_version.*/set(PYGTK_FOUND TRUE)/g' grc/CMakeLists.txt
+    find . -name "CMakeLists.txt" -exec sed -i '1iadd_compile_options($<$<COMPILE_LANGUAGE:CXX>:-std=c++11>)' "{}" ";"
   '';
 
   # Framework path needed for qwt6_qt4 but not qwt5