IOS Build settings IL2CPP disabled, Xcode error "Undefined symbol: _UnityPluginUnload"

Unity editor 2018.3.0f2 while building to ios , xcode giving an error “Undefined symbol: _UnityPluginUnload”
Its working fine from starting.after i made backup of project this build error occurred.!
Any idea why this happens.
135928-ios.jpg

The fix:
https://developer.vuforia.com/forum/unity/linker-errors-vuforia-81-unity-201830f2