Nerves app not building correctly in umbrella projects

[stwf]

When a Nerves app is built inside an umbrella app the mix.exs file will reference the config files located at the root of the umbrella app. But the nerves.new script doesn't place the config files there.

The app will build but fail silently since the Nerves config.exs isn't appended to the app config.exs the host.exs or target.exs files aren't referenced.

I made a PR that fixes it in 1 way. Hope that helps!

#261

Environment

• Elixir version (elixir -v): 1.14.2
• Nerves environment:

  Pkg:         nerves_system_br
  Vsn:         1.22.5
  Type:        system_platform
  BuildRunner: {nil, []}

  Pkg:         nerves_system_rpi0
  Vsn:         1.22.2
  Type:        system
  BuildRunner: {Nerves.Artifact.BuildRunners.Docker, [make_args: ["source", "all", "legal-info"]]}

  Pkg:         nerves_toolchain_armv6_nerves_linux_gnueabihf
  Vsn:         1.8.0
  Type:        toolchain
  BuildRunner: {Nerves.Artifact.BuildRunners.Local, []}

  Pkg:         nerves_toolchain_ctng
  Vsn:         1.9.3
  Type:        toolchain_platform
  BuildRunner: {nil, []}

I think the main thing is to use the latest version of the phx_new archive, since they older versions had issues with umbrella projects.