cmake: GH PR17, Add DisplayServer variables for the WSI interfaces
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5be176b..e48114b 100755
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -27,22 +27,24 @@
     option(BUILD_WSI_WAYLAND_SUPPORT "Build Wayland WSI support" OFF)
     option(BUILD_WSI_MIR_SUPPORT "Build Mir WSI support" OFF)
 
-    set(DisplayServer Xcb)
-
     if (BUILD_WSI_XCB_SUPPORT)
         add_definitions(-DVK_USE_PLATFORM_XCB_KHR)
+        set(DisplayServer Xcb)
     endif()
 
     if (BUILD_WSI_XLIB_SUPPORT)
         add_definitions(-DVK_USE_PLATFORM_XLIB_KHR)
+        set(DisplayServer XLib)
     endif()
 
     if (BUILD_WSI_WAYLAND_SUPPORT)
         add_definitions(-DVK_USE_PLATFORM_WAYLAND_KHR)
+        set(DisplayServer Wayland)
     endif()
 
     if (BUILD_WSI_MIR_SUPPORT)
         add_definitions(-DVK_USE_PLATFORM_MIR_KHR)
+        set(DisplayServer Mir)
     endif()
 else()
     message(FATAL_ERROR "Unsupported Platform!")