Index: cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- cmake/modules/HandleLLVMOptions.cmake
+++ cmake/modules/HandleLLVMOptions.cmake
@@ -521,6 +521,7 @@
 if (LLVM_ENABLE_WARNINGS AND (LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
   append("-Wall -W -Wno-unused-parameter -Wwrite-strings" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
   append("-Wcast-qual" CMAKE_CXX_FLAGS)
+  append("-Wno-error=cast-qual" CMAKE_CXX_FLAGS)
 
   # Turn off missing field initializer warnings for gcc to avoid noise from
   # false positives with empty {}. Turn them on otherwise (they're off by