backport(9.0): Fix runtime architecture detection logic in ANCM.

[DeagleGross]

Description

Backport of #63652 to net9.0

A change (#61894) improved algorithm to determine the architecture of a binary by switching away from GetBinaryTypeW (which seems to load the exe into executable space which might trigger custom windows policies). It was backported to net9.0: #62038.

However, we spotted that sometimes function incorrectly chooses a binary of an incompatible architecture, resulting in crashing site load.

Current change specifically checks for a full compatibility of bitness and architecture.

Fixes #63650

Customer Impact

For example users hosting x86 app on x64 machine / x64 app on arm64 machine are impacted unless current change is merged and used.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

Impacts users who are using different process architecture then what where.exe outputs trying to find dotnet binary. It takes OS / process / dotnet arch installed combination to affect the behavior.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

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[Copilot]

Pull Request Overview

This PR backports a fix for runtime architecture detection logic in the ASP.NET Core Module (ANCM) to .NET 9.0. The changes replace the previous boolean-based x64 detection with a more comprehensive processor architecture system that supports x86, AMD64, and ARM64 architectures.

• Introduces a new ProcessorArchitecture enum to handle multiple architecture types instead of just x64/x86
• Replaces runtime PE header magic number detection with compile-time architecture detection
• Updates architecture matching logic to use the new enum-based system for finding compatible dotnet.exe instances

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
ProcessorArchitecture.h	New header defining ProcessorArchitecture enum and string conversion utility
HostFxrResolver.h	Updates method signature from IsX64 to GetFileProcessorArchitecture
HostFxrResolver.cpp	Refactors architecture detection logic and improves PE header parsing
Environment.h	Adds GetCurrentProcessArchitecture method declaration
Environment.cpp	Implements compile-time architecture detection using preprocessor macros

[Copilot]

Use static_assert(false) with a dependent type to avoid immediate compilation failure. Consider using static_assert(sizeof(void*) == 0, ...) or a template-dependent expression to ensure this only triggers when the code path is actually instantiated.

Suggested change

	static_assert(false, "Unknown target architecture");
	static_assert(sizeof(void*) == 0, "Unknown target architecture");

[danmoseley]

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