kmscube: pull upstream fix for -fno-common toolchains

Without the change build against upstream gcc-10 fails as:

    ld: kmscube-cube-tex.o:/build/kmscube-9dcce71/cube-tex.c:48: multiple definition of `gl';
      kmscube-cube-smooth.o:/build/kmscube-9dcce71/cube-smooth.c:40: first defined here

pkgs/os-specific/linux/kmscube/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchgit, autoreconfHook, libdrm, libX11, libGL, mesa, pkg-config }:
+{ lib, stdenv, fetchgit, fetchpatch, autoreconfHook, libdrm, libX11, libGL, mesa, pkg-config }:
 
 stdenv.mkDerivation {
   pname = "kmscube";
@@ -10,6 +10,15 @@ stdenv.mkDerivation {
     sha256 = "1q5b5yvyfj3127385mp1bfmcbnpnbdswdk8gspp7g4541xk4k933";
   };
 
+  patches = [
+    # Pull upstream patch for -fno-common toolchains.
+    (fetchpatch {
+      name = "fno-common.patch";
+      url = "https://gitlab.freedesktop.org/mesa/kmscube/-/commit/908ef39864442c0807954af5d3f88a3da1a6f8a5.patch";
+      sha256 = "1gxn3b50mvjlc25234839v5z29r8fd9di4176a3yx4gbsz8cc5vi";
+    })
+  ];
+
   nativeBuildInputs = [ autoreconfHook pkg-config ];
   buildInputs = [ libdrm libX11 libGL mesa ];