`lld` and (newer) `ld.bfd` and `ld.gold` support a `--dependency-file=` flag to dump out depfiles. We should hook this up in the Ninja and Makefiles generators. See [this message on the `gn-dev` list](https://groups.google.com/a/chromium.org/g/gn-dev/c/sN09GYS1ufE/m/D5p9tl8QAwAJ). Cc: @kyle.edwards @brad.king @marc.chevrier