Document DOTNET_CLI_ENABLEAOT environment variable (NativeAOT CLI fast path, enabled by default)

[baronfel]

Summary

Starting with the .NET SDK preview that resolves dotnet/sdk#55078, the SDK ships a NativeAOT-compiled CLI entry point that handles common dotnet commands (parsing, --version, --info, and a growing set of built-in/external commands) on a fast native path, transparently falling back to the managed CLI for anything it does not handle.

This fast path is controlled by the DOTNET_CLI_ENABLEAOT environment variable, and it is now enabled by default. Users who need to bypass it (for example, to diagnose a suspected behavioral difference) can opt out by setting the variable to a falsy value.

This variable is not currently documented in the dotnet environment variables reference.

Requested documentation

Add a DOTNET_CLI_ENABLEAOT entry to docs/core/tools/dotnet-environment-variables.md covering:

• Purpose: enables/disables the NativeAOT CLI command-handling fast path.
• Default: enabled.
• Accepted values:
  • Enable (default): unset, or true / 1 / yes / on
  • Disable (opt out): false / 0 / no / off
• Behavior when disabled: every invocation is routed to the managed CLI, matching pre-default behavior.

References

• Tracking issue: Enable NAOT command handling by default sdk#55078
• Design doc: src/Cli/dotnet-aot/DESIGN.md in dotnet/sdk