File llvm-remove-clang-only-flags.patch of Package llvm8

Index: llvm-8.0.0rc3.src/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm-8.0.0rc3.src.orig/cmake/modules/HandleLLVMOptions.cmake
+++ llvm-8.0.0rc3.src/cmake/modules/HandleLLVMOptions.cmake
@@ -413,8 +413,6 @@ if( MSVC )
 elseif( LLVM_COMPILER_IS_GCC_COMPATIBLE )
   append_if(LLVM_ENABLE_WERROR "-Werror" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
   append_if(LLVM_ENABLE_WERROR "-Wno-error" CMAKE_REQUIRED_FLAGS)
-  add_flag_if_supported("-Werror=date-time" WERROR_DATE_TIME)
-  add_flag_if_supported("-Werror=unguarded-availability-new" WERROR_UNGUARDED_AVAILABILITY_NEW)
   if (LLVM_ENABLE_CXX1Y)
     check_cxx_compiler_flag("-std=c++1y" CXX_SUPPORTS_CXX1Y)
     append_if(CXX_SUPPORTS_CXX1Y "-std=c++1y" CMAKE_CXX_FLAGS)
@@ -586,7 +584,6 @@ if (LLVM_ENABLE_WARNINGS AND (LLVM_COMPI
   endif()
 
   add_flag_if_supported("-Wimplicit-fallthrough" IMPLICIT_FALLTHROUGH_FLAG)
-  add_flag_if_supported("-Wcovered-switch-default" COVERED_SWITCH_DEFAULT_FLAG)
   append_if(USE_NO_UNINITIALIZED "-Wno-uninitialized" CMAKE_CXX_FLAGS)
   append_if(USE_NO_MAYBE_UNINITIALIZED "-Wno-maybe-uninitialized" CMAKE_CXX_FLAGS)