xnee: pull fix pending upstream inclusion for -fno-common toolchain support

Without the change build fails as:

    $ nix build -L --impure --expr 'with import ./. {}; xnee.overrideAttrs (oa: {   NIX_CFLAGS_COMPILE = (oa.NIX_CFLAGS_COMPILE or "") + "-fno-common"; })'
    ...
    ld: .libs/xnee_xinput.o:/build/xnee-3.19/libxnee/src/../include/libxnee/xnee_internal.h:117:
      multiple definition of `xnee_mode';

pkgs/tools/X11/xnee/default.nix

@@ -1,4 +1,4 @@
-{ fetchurl, lib, stdenv, libX11, xorgproto, libXext, libXtst
+{ fetchurl, fetchpatch, lib, stdenv, libX11, xorgproto, libXext, libXtst
 , gtk2, libXi, pkg-config, texinfo }:
 
 stdenv.mkDerivation rec {
@@ -10,7 +10,17 @@ stdenv.mkDerivation rec {
     sha256 = "04n2lac0vgpv8zsn7nmb50hf3qb56pmj90dmwnivg09gyrf1x92j";
   };
 
-  patchPhase =
+  patches = [
+    # Pull fix pending upstream inclusion for -fno-common
+    # toolchain support: https://savannah.gnu.org/bugs/?58810
+    (fetchpatch {
+      name = "fno-common.patch";
+      url = "https://savannah.gnu.org/bugs/download.php?file_id=49534";
+      sha256 = "04j2cjy2yaiigg31a6k01vw0fq19yj3zpriikkjcz9q4ab4m5gh2";
+    })
+  ];
+
+  postPatch =
     '' for i in `find cnee/test -name \*.sh`
        do
          sed -i "$i" -e's|/bin/bash|${stdenv.shell}|g ; s|/usr/bin/env bash|${stdenv.shell}|g'