Publish Cargo outputs through MSBuild

[David Federman (dfederm)]

Summary

This updates the Cargo SDK so generated primary outputs are published through the evaluated MSBuild OutputPath instead of staying only in Cargo’s target tree. That lets dependent projects consume Rust-produced artifacts through normal MSBuild project-reference contracts while keeping Cargo intermediates out of the public output directory.

The SDK still honors CargoOutputDir overrides and ordinary local Cargo builds. The new contract also supports explicit output declarations and automatic discovery for the common cases the SDK can safely publish.

Why this is safe

• Cargo’s full target/intermediate tree still stays under the Cargo output directory; only selected primary outputs are staged for MSBuild consumption.
• Explicit output items override discovery, so unusual or renamed outputs can be declared without changing the default behavior.
• The publication point is integrated so outputs exist before project completion and are visible to downstream project-reference consumers.
• Package/native consumer behavior was verified, including a real VC++ project-reference scenario using a staged import library.

Validation

Test / build	Result
src/Cargo/Microsoft.Build.Cargo.csproj Release build	pass
Cargo unit test matrix	280/280 passed
Packaged fake-Cargo integration	pass
Real VC++ project-reference consumer	pass
High-volume stream + process-tree timeout coverage	pass
Incremental + clean validation	pass

Out of scope

• This does not move the full Cargo target tree into OutputPath.
• This does not change downstream sample/workaround projects beyond the SDK contract itself.