polybar: nuke reference to stdenv.cc, small clean up

pkgs/applications/misc/polybar/default.nix

@@ -64,10 +64,15 @@ stdenv.mkDerivation rec {
       (if i3Support || i3GapsSupport then makeWrapper else null)
     ];
 
-    fixupPhase = if (i3Support || i3GapsSupport) then ''
-    wrapProgram $out/bin/polybar \
-      --prefix PATH : "${if i3Support then i3 else i3-gaps}/bin"
-  '' else null;
+    postConfigure = ''
+      substituteInPlace ../include/settings.hpp --replace \
+        "${stdenv.cc}" "${stdenv.cc.name}"
+    '';
+
+    postInstall = if (i3Support || i3GapsSupport) then ''
+      wrapProgram $out/bin/polybar \
+        --prefix PATH : "${if i3Support then i3 else i3-gaps}/bin"
+    '' else "";
 
     nativeBuildInputs = [
       cmake pkgconfig