[gn build] Port fa79e0a

Author: llvmgnsyncbot

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

@@ -1361,6 +1361,7 @@ if (current_toolchain == default_toolchain) {
       "__ranges/data.h",
       "__ranges/drop_view.h",
       "__ranges/drop_while_view.h",
+      "__ranges/elements_of.h",
       "__ranges/elements_view.h",
       "__ranges/empty.h",
       "__ranges/empty_view.h",