Fixed visual studio errors about openmp compiler flags not being right.

dlib/CMakeLists.txt

@@ -662,8 +662,10 @@ if (NOT TARGET dlib)
       if (OPENMP_FOUND)
          # Enable OpenMP
          target_compile_options(dlib PUBLIC ${OpenMP_CXX_FLAGS}) 
+         if (NOT MSVC)
             target_link_libraries(dlib PUBLIC ${OpenMP_CXX_FLAGS}) 
          endif()
+      endif()
       if (UNIX AND NOT DLIB_IN_PROJECT_BUILD)
          if (DLIB_USE_CUDA)
             cuda_add_library(dlib_shared SHARED ${source_files} )
@@ -681,9 +683,11 @@ if (NOT TARGET dlib)
          if (OPENMP_FOUND)
             # Enable OpenMP
             target_compile_options(dlib_shared PUBLIC ${OpenMP_CXX_FLAGS}) 
+            if (NOT MSVC)
                target_link_libraries(dlib_shared PUBLIC ${OpenMP_CXX_FLAGS}) 
             endif()
          endif()
+      endif()
 
    endif ()  ##### end of if NOT DLIB_ISO_CPP_ONLY ##########################################################