[gn build] Port 2039a51 (#193861)

Author: nico

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

@@ -1393,6 +1393,7 @@ if (current_toolchain == default_toolchain) {
       "__ranges/empty_view.h",
       "__ranges/enable_borrowed_range.h",
       "__ranges/enable_view.h",
+      "__ranges/enumerate_view.h",
       "__ranges/filter_view.h",
       "__ranges/from_range.h",
       "__ranges/iota_view.h",