[gn build] Port 0e34f3f

Author: llvmgnsyncbot

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

@@ -284,11 +284,13 @@ if (current_toolchain == default_toolchain) {
       "__atomic/atomic_sync.h",
       "__atomic/check_memory_order.h",
       "__atomic/contention_t.h",
-      "__atomic/cxx_atomic_impl.h",
       "__atomic/fence.h",
       "__atomic/is_always_lock_free.h",
       "__atomic/kill_dependency.h",
       "__atomic/memory_order.h",
+      "__atomic/support.h",
+      "__atomic/support/c11.h",
+      "__atomic/support/gcc.h",
       "__atomic/to_gcc_order.h",
       "__bit/bit_cast.h",
       "__bit/bit_ceil.h",