fix(views/kit): allow setting localSystem when using tvl-kit r/5873

Because the passing around of externalArgs only happened in the readTree
instantiation in the repo root default.nix, but not in views/kit/
default.nix, it was not possible to get tvl-kit to instantiate the
bundled nixpkgs with a custom system.

This fixes invocations like

```
tvl-kit = import (sources.tvl-kit) { localSystem = "aarch64-linux"; };
```

Change-Id: I3a633e4d695d266459400ba74fc0693ecc5bfb54
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8197
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

0 files changed, 0 insertions, 0 deletions