Fix stand-alone build

CMake Error at CMakeLists.txt:40 (add_executable):
  Cannot find source file:

    /home/bernd/buildroot/output/build/host-kodi-texturepacker-18.4-Leia/tools/depends/native/TexturePacker/xbmc/guilib/XBTF.cpp

  Tried extensions .c .C .c++ .cc .cpp .cxx .cu .m .M .mm .h .hh .h++ .hm
  .hpp .hxx .in .txx

CMake Error at CMakeLists.txt:40 (add_executable):
  No SOURCES given to target: TexturePacker

Downloaded from
https://github.com/LibreELEC/LibreELEC.tv/blob/master/packages/mediacenter/kodi/patches/kodi-100.25-hack-fix-texture-packer-cmake-source-dir.patch

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>

diff -Naur a/tools/depends/native/TexturePacker/CMakeLists.txt b/tools/depends/native/TexturePacker/CMakeLists.txt
--- a/tools/depends/native/TexturePacker/CMakeLists.txt	2016-12-23 17:10:28.593185862 +0000
+++ b/tools/depends/native/TexturePacker/CMakeLists.txt	2016-12-23 17:10:39.469253011 +0000
@@ -1,3 +1,5 @@
+set(CMAKE_SOURCE_DIR ${CMAKE_SOURCE_DIR}/../../../..)
+
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake/modules)
 
 if(APPLE)