[release/9.0.1xx] Fix incorrect apphost being used when publishing for self-contained single-file with NoBuild=true

[github-actions]

Backport of #45159 to release/9.0.1xx

/cc @marcpopMSFT @elinor-fung

Customer Impact

• Customer reported
• Found internally

Reported via:

• Developer Community: https://developercommunity.visualstudio.com/t/Single-file-self-contained-failing-after/10794374.
• GitHub: publishsinglefile causes runtime failure of hostpolicy.dll not found for dotnet 9.0.100 #44992, Self-contained single-file program, published with --no-build option, needs .NET to be installed #45230

Customers using the --no-build option to publish a single-file self-contained application end up with broken publish output. The published app will fail to launch. This significantly impacts source-build users.

This is due to a target used for determining configuration for apphost creation (which can occur in both build and publish) not getting chained when NoBuild=true. Publishing with --no-build ended up using the regular apphost (instead of the single-file, self-contained one), resulting in an app that was configured to be self-contained but did not actually have the runtime as part of itself.

A workaround is to either edit the app's project file to explicitly chain in a target or stop using --no-build.

Regression

• Yes
• No

Regression from .NET 8. Logic around configuring apphost creation used to be repeated in separate places. In .NET 9, we consolidated it into one target, but missed making sure that target was pulled in when publishing with NoBuild=true.

Testing

Manual testing with customer repro. Added automated test.

Risk

Low. The fix chains in an existing target such that it will be still be run when NoBuild=true (the --no-build option).

[marcpopMSFT]

@elinor-fung can you add the tactics template and mark it servicing-consider when done? We'll discuss in Thursday's tactics.

[elinor-fung]

Filled out template and added servicing-consider label.