BUG: fixed build files for Vulkan GUI

Source/GUIOverlay/CMakeLists.txt

@@ -6,11 +6,11 @@ include(imstkAddLibrary)
 file (GLOB_RECURSE GUI_h_files "${CMAKE_CURRENT_SOURCE_DIR}/imstk*.h")
 file (GLOB_RECURSE GUI_cpp_files "${CMAKE_CURRENT_SOURCE_DIR}/imstk*.cpp")
 
-if( iMSTK_USE_VULKAN )
+if( iMSTK_USE_Vulkan )
   set (IMPLEMENTATION_H_FILES
     ${imgui_INCLUDE_DIR}/examples/imgui_impl_vulkan.h
     ${imgui_INCLUDE_DIR}/examples/imgui_impl_glfw.h)
-  set (IMPLENTATION_CPP_FILES
+  set (IMPLEMENTATION_CPP_FILES
     ${imgui_INCLUDE_DIR}/examples/imgui_impl_vulkan.cpp
     ${imgui_INCLUDE_DIR}/examples/imgui_impl_glfw.cpp)
 endif()