Support multiple binary logs from command line arguments

[Copilot]

MSBuild previously accepted multiple -bl flags but only wrote the last-specified binlog, preventing tools like CodeQL from controlling binlog output locations when users also specify binlogs.

Changes

Smart multi-binlog handling

• Analyzes all -bl parameter sets to detect configuration differences beyond file paths
• Same configuration: Single logger writes once, then copies to all destinations atomically on shutdown (ensures consistency)
• Different configurations: Creates separate logger instances to respect each configuration (e.g., ProjectImports=None vs ProjectImports=Embed)

BinaryLogger enhancements

• Added AdditionalFilePaths property to track copy destinations
• Added ExtractFilePathFromParameters() to parse file paths from parameter strings
• Added ExtractNonPathParameters() to extract and normalize configuration options
• Enhanced Shutdown() to copy binlog to additional paths with error handling

Command-line processing

• Updated ProcessBinaryLogger() in XMake.cs with configuration detection logic
• Deduplicates identical file paths across multiple flags

Example

# Same configuration - optimized single write + copy
msbuild project.csproj /bl:1.binlog /bl:2.binlog /bl:3.binlog

# Different configurations - separate loggers
msbuild project.csproj /bl:full.binlog /bl:minimal.binlog;ProjectImports=None

Both approaches produce identical binlogs when configurations match, and distinct binlogs when configurations differ.

Original prompt

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This section details on the original issue you should resolve

<issue_title>MSBuild.exe should support writing multiple binlogs if supplied as part of command line arguments</issue_title>
<issue_description>### Summary

Today it's possible to provide the -bl flag multiple times, but the behavior of the engine is that the last-provided flag wins:

> dotnet build -bl:1.binlog -bl:2.binlog
Restore complete (0.1s)
    info NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
  lib2 net10.0 succeeded (0.1s) → D:\Code\scratch\bleh\lib2\bin\Debug\net10.0\lib2.dll
  bleh net10.0 succeeded (0.1s) → bin\Debug\net10.0\bleh.dll

Build succeeded in 0.5s
> ls *.binlog

    Directory: D:\Code\scratch\bleh\lib

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---          10/29/2025 11:14 AM         454756 2.binlog

This is confusing, and in extreme cases can mean that tools that need binlogs and provide them via things like response files can be overridden by a users invocation.

Background and Motivation

The inability to write more than one binlog file means that tools like codeql have a harder time adopting binlog usage for C# code analysis, because they can't control where the binlog is generated.

Proposed Feature

The command-line handling should accept multiple bl flags, resolve them into their distinct binlog filenames, ensure that set is distinct, and then the binary logger should be able to write binary logs to all of those specified files.

This file writing could be done in two ways (at least)

• multiple independent writers, each writing to a separate file
• one writer, writing the binlog file to a temp location and then atomically copying that file to the various destinations at build-finish

We should use the second option for consistency.

Alternative Designs

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes MSBuild.exe should support writing multiple binlogs if supplied as part of command line arguments #12705

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[baronfel]

@rainersigwald is this the binlog API that end-users end up using? If so we probably want to think about this exposed shape a bit more and force this stuff into 'normal 'logger parameter parsing instead.