diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -130,6 +130,10 @@
     set(export_file_linker_flag "${CMAKE_CURRENT_BINARY_DIR}/${native_export_file}")
     if(MSVC)
       set(export_file_linker_flag "/DEF:\"${export_file_linker_flag}\"")
+    elseif(WIN32)
+      # If we're compiling on Windows and the compiler is not Visual Studio,
+      # then tell it to forward the `/DEF` flag to the linker.
+      set(export_file_linker_flag "-Wl,/DEF:\"${export_file_linker_flag}\"")
     endif()
     set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                  LINK_FLAGS " ${export_file_linker_flag}")