Index: cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- cmake/modules/HandleLLVMOptions.cmake
+++ cmake/modules/HandleLLVMOptions.cmake
@@ -312,7 +312,7 @@
   # Pass -mbig-obj to mingw gas on Win64. COFF has a 2**16 section limit, and
   # on Win64, every COMDAT function creates at least 3 sections: .text, .pdata,
   # and .xdata.
-  if (CMAKE_SIZEOF_VOID_P EQUAL 8)
+  if (CMAKE_SIZEOF_VOID_P EQUAL 8 AND NOT "${CMAKE_ASM_COMPILER_ID}" MATCHES "Clang")
     append("-Wa,-mbig-obj" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
   endif()
 endif()