[gn build] Port 4e112e5

Author: llvmgnsyncbot

llvm/utils/gn/secondary/libcxx/include/BUILD.gn

@@ -886,6 +886,7 @@ if (current_toolchain == default_toolchain) {
       "__type_traits/is_trivially_lexicographically_comparable.h",
       "__type_traits/is_trivially_move_assignable.h",
       "__type_traits/is_trivially_move_constructible.h",
+      "__type_traits/is_trivially_relocatable.h",
       "__type_traits/is_unbounded_array.h",
       "__type_traits/is_union.h",
       "__type_traits/is_unsigned.h",