freenect: fix

As mentioned in the linked PKGBUILD, the proper variable is
GLUT_LIBRARIES these days.

pkgs/development/libraries/freenect/default.nix

@@ -18,6 +18,11 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ cmake pkg-config ];
 
+  # see https://aur.archlinux.org/cgit/aur.git/commit/PKGBUILD?h=libfreenect&id=0d17db49ba64bcb9e3a4eed61cf55c9a5ceb97f1
+  patchPhase = lib.concatMapStrings (x: ''
+    substituteInPlace ${x} --replace "{GLUT_LIBRARY}" "{GLUT_LIBRARIES}"
+  '') [ "examples/CMakeLists.txt" "wrappers/cpp/CMakeLists.txt" ];
+
   meta = {
     description = "Drivers and libraries for the Xbox Kinect device on Windows, Linux, and macOS";
     homepage = "http://openkinect.org";