Use file symlink instead of directory for STB library.

Fix #1330.

Source/ThirdParty/STB/CMakeLists.txt

@@ -28,4 +28,4 @@ add_custom_target (${TARGET_NAME} ALL)   # Dummy target just so that its post-bu
 set (STATIC_LIBRARY_TARGETS ${STATIC_LIBRARY_TARGETS} ${TARGET_NAME} PARENT_SCOPE)
 
 # Install headers for building the Urho3D library
-install_header_files (DIRECTORY ./ DESTINATION ${DEST_INCLUDE_DIR}/ThirdParty/STB FILES_MATCHING PATTERN *.h)  # Note: the trailing slash is significant
+install_header_files (DIRECTORY ./ DESTINATION ${DEST_INCLUDE_DIR}/ThirdParty/STB FILES_MATCHING PATTERN *.h USE_FILE_SYMLINK BUILD_TREE_ONLY)  # Note: the trailing slash is significant

Source/Tools/SpritePacker/CMakeLists.txt

@@ -26,7 +26,5 @@ set (TARGET_NAME SpritePacker)
 # Define source files
 define_source_files ()
 
-include_directories(../../ThirdParty/STB)
-
 # Setup target
 setup_executable (TOOL)

Source/Tools/SpritePacker/SpritePacker.cpp

@@ -36,7 +36,7 @@
 
 #define STBRP_LARGE_RECTS
 #define STB_RECT_PACK_IMPLEMENTATION
-#include "stb_rect_pack.h"
+#include <STB/stb_rect_pack.h>
 
 #include <Urho3D/DebugNew.h>