Find only shared IE libraries, not plugins

cmake/OpenCVDetectInferenceEngine.cmake

@@ -62,7 +62,13 @@ function(add_custom_ie_build _inc _lib _lib_rel _lib_dbg _msg)
     if(find_prefix STREQUAL "_empty_")  # foreach doesn't iterate over empty elements
       set(find_prefix "")
     endif()
-    foreach(find_suffix ${CMAKE_FIND_LIBRARY_SUFFIXES})
+    if(NOT DEFINED INFERENCE_ENGINE_FIND_LIBRARY_SUFFIXES)  # allow custom override
+      set(INFERENCE_ENGINE_FIND_LIBRARY_SUFFIXES ${CMAKE_FIND_LIBRARY_SUFFIXES})
+      if(APPLE)
+        ocv_list_filterout(INFERENCE_ENGINE_FIND_LIBRARY_SUFFIXES "^.so$")  # skip plugins (can't be linked)
+      endif()
+    endif()
+    foreach(find_suffix ${INFERENCE_ENGINE_FIND_LIBRARY_SUFFIXES})
       ocv_ie_find_extra_libraries("${find_prefix}" "${find_suffix}")
     endforeach()
     if(NOT CMAKE_FIND_LIBRARY_SUFFIXES)