added AntTweakBar requirement to glow-extras-glfw

CMakeLists.txt

@@ -53,10 +53,14 @@ else()
 endif()
 
 # GLFW App
-# requires 'aion'
+# requires 'aion' and 'AntTweakBar'
 if (TARGET aion)
+    if (TARGET AntTweakBar)
         add_subdirectory(glfw)
         target_link_libraries(glow-extras PUBLIC glow-extras-glfw)
+    else()
+        message(STATUS "target 'AntTweakBar' not found, disabling glow-extras-glfw")
+    endif()
 else()
     message(STATUS "target 'aion' not found, disabling glow-extras-glfw")
 endif()