Unity-Android problems with plugins in unity 2018.2.19f1

We are getting the following error when trying to use OpenCV libraries and some native libraries created by us for Android using Unity. The point is that I have updated Unity after a long time and in the previous version it didn't give me any problem:

 Exception: Unknown CPU architecture  for library 
     Assets/Plugins/Android/libopencv_bioinspired.a
     UnityEditor.Android.PostProcessor.Tasks.NativePlugins.ProcessPlugin 
     (UnityEditor.Android.PostProcessor.PostProcessorContext context, 
     System.String pluginPath, System.String pluginTargetCPU)
     UnityEditor.Android.PostProcessor.Tasks.NativePlugins.Execute 
     (UnityEditor.Android.PostProcessor.PostProcessorContext context)
     UnityEditor.Android.PostProcessor.PostProcessRunner.RunAllTasks 
     (UnityEditor.Android.PostProcessor.PostProcessorContext context)
     UnityEditor.Android.PostProcessAndroidPlayer.PostProcess (BuildTarget 
     target, System.String stagingAreaData, System.String stagingArea, 
     System.String playerPackage, System.String installPath, System.String 
     companyName, System.String productName, BuildOptions options, 
     UnityEditor.RuntimeClassRegistry usedClassRegistry, 
     UnityEditor.Build.Reporting.BuildReport report)
     UnityEditor.Android.AndroidBuildPostprocessor.PostProcess 
     (BuildPostProcessArgs args, UnityEditor.BuildProperties& outProperties)
     UnityEditor.PostprocessBuildPlayer.Postprocess (BuildTargetGroup 
     targetGroup, BuildTarget target, System.String installPath, System.String 
     companyName, System.String productName, Int32 width, Int32 height, 
     BuildOptions options, UnityEditor.RuntimeClassRegistry usedClassRegistry, 
     UnityEditor.Build.Reporting.BuildReport report) (at 
     C:/buildslave/unity/build/Editor/Mono/- 
     - BuildPipeline/PostprocessBuildPlayer.cs:287)
     UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)