FindMatlab: Fix Matlab_LIBRARIES for MCR

In commit bda5e2ac8f (FindMatlab: Only include engine and dataarray
libraries if they are found, 2020-12-11, v3.20.0-rc1~297^2~1) we fixed
the imported target to contain optional libraries only if they are
found.  Do the same for `Matlab_LIBRARIES`.

Modules/FindMatlab.cmake

@@ -1854,8 +1854,15 @@ endif()
 
 set(Matlab_LIBRARIES
   ${Matlab_MEX_LIBRARY} ${Matlab_MX_LIBRARY}
-  ${Matlab_ENG_LIBRARY} ${Matlab_MAT_LIBRARY}
-  ${Matlab_DATAARRAY_LIBRARY} ${Matlab_ENGINE_LIBRARY})
+  ${Matlab_ENG_LIBRARY} ${Matlab_MAT_LIBRARY})
+
+if(Matlab_ENGINE_LIBRARY)
+  list(APPEND Matlab_LIBRARIES ${Matlab_ENGINE_LIBRARY})
+endif()
+
+if(Matlab_DATAARRAY_LIBRARY)
+  list(APPEND Matlab_LIBRARIES ${Matlab_DATAARRAY_LIBRARY})
+endif()
 
 find_package_handle_standard_args(
   Matlab