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
@@ -118,7 +118,7 @@
       set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                    LINK_FLAGS "  -Wl,--version-script,\"${CMAKE_CURRENT_BINARY_DIR}/${native_export_file}\"")
     endif()
-  else()
+  elseif(WIN32)
     set(native_export_file "${target_name}.def")
 
     add_custom_command(OUTPUT ${native_export_file}
@@ -129,7 +129,18 @@
       COMMENT "Creating export file for ${target_name}")
     set(export_file_linker_flag "${CMAKE_CURRENT_BINARY_DIR}/${native_export_file}")
     if(MSVC)
+      # cl.exe or clang-cl, i.e. MSVC style command line interface
       set(export_file_linker_flag "/DEF:\"${export_file_linker_flag}\"")
+    elseif(CMAKE_CXX_SIMULATE_ID STREQUAL "MSVC")
+      # clang in msvc mode, calling a link.exe/lld-link style linker
+      set(export_file_linker_flag "-Wl,/DEF:\"${export_file_linker_flag}\"")
+    elseif(MINGW)
+      # ${export_file_linker_flag}, which is the plain file name, works as is
+      # when passed to the compiler driver, which then passes it on to the
+      # linker as an input file.
+      set(export_file_linker_flag "\"${export_file_linker_flag}\"")
+    else()
+      message(FATAL_ERROR "Unsupported Windows toolchain")
     endif()
     set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                  LINK_FLAGS " ${export_file_linker_flag}")