iOS unable to share configuration between builds

[gtbuchanan]

I have some configuration that should only be applied to the Release build. However, all other configuration should be shared between the Debug and Release builds. When defining configuration for a specific build, the more generic configuration appears to stop working. For example, this successfully sets the bundle ID:

platforms:
  ios:
    bundleId: com.example.app

This sets the Release-specific settings, but the bundle ID stops being set:

platforms:
  ios:
    bundleId: com.example.app
    targets:
      builds:
        Release:
          buildSettings:
            CODE_SIGN_STYLE: Manual
            CODE_SIGN_IDENTITY: iPhone Distribution
            PROVISIONING_PROFILE_SPECIFIER: My App

I've tried to workaround this problem by using YAML merging:

platforms:
  ios:
    targets:
      builds:
        Debug: &iosDefaults
          bundleId: com.example.app
        Release:
          <<: *iosDefaults
          buildSettings:
            CODE_SIGN_STYLE: Manual
            CODE_SIGN_IDENTITY: iPhone Distribution
            PROVISIONING_PROFILE_SPECIFIER: My App

but that results in a warning and the Release configuration not being applied:

run ios <<
[warn] Unsupported configuration option ios.<<. Skipping

Is this a bug? Is there a way to achieve this without duplicating the configuration?