[CMake] Error when LTO and lld are enabled on Darwin

lld on Darwin does not currently support LTO.

Differential Revision: https://reviews.llvm.org/D26715

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@287256 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/modules/HandleLLVMOptions.cmake

@@ -96,6 +96,9 @@ set(LTDL_SHLIB_EXT ${CMAKE_SHARED_LIBRARY_SUFFIX})
 set(LLVM_PLUGIN_EXT ${CMAKE_SHARED_LIBRARY_SUFFIX})
 
 if(APPLE)
+  if(LLVM_ENABLE_LLD AND LLVM_ENABLE_LTO)
+    message(FATAL_ERROR "lld does not support LTO on Darwin")
+  endif()
   # Darwin-specific linker flags for loadable modules.
   set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -Wl,-flat_namespace -Wl,-undefined -Wl,suppress")
 endif()