[Android][CoreCLR] Use runtimeconfig.bin for runtime configuration lookup in ApkBuilder

[Copilot]

The AndroidAppBuilder was incorrectly looking for {ProjectName}.runtimeconfig.json when the actual generated file is named {AssemblyName}.runtimeconfig.json, causing the CoreCLR Android test host to fail finding the runtime configuration file.

Problem

When building Android apps and especially when running tests:

• The assembly name differs from the project name
• For tests, mainLibraryFileName is set to AndroidTestRunner.dll
• Looking for AndroidTestRunner.runtimeconfig.json for all tests is incorrect as each test project has its own configuration
• This resulted in errors like: Could not find file 'HelloAndroid.runtimeconfig.json'

Solution

Modified the ParseRuntimeConfigProperties method to use the standardized runtimeconfig.bin file instead of trying to guess the correct JSON filename. This binary file is created by MSBuild's RuntimeConfigParserTask and contains the same configuration properties in a binary format.

The implementation uses the existing BlobReader from System.Reflection.Metadata to read the binary format, which provides the necessary ReadCompressedInteger() and ReadSerializedString() methods that mirror the BlobBuilder write operations.

Before:

string runtimeConfigPath = Path.Combine(AppDir, $"{ProjectName}.runtimeconfig.json");

After:

string runtimeConfigPath = Path.Combine(AppDir, "runtimeconfig.bin");

The solution maintains the same functionality of extracting configProperties for the CoreCLR Android template while working reliably for both apps and test scenarios.

Fixes #118162.

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[davidnguyen-tech]

/azp run runtime-android,runtime-androidemulator

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[davidnguyen-tech]

/azp run runtime-android,runtime-androidemulator

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[davidnguyen-tech]

LGTM

[Copilot]

Pull Request Overview

This PR fixes a critical bug in the AndroidAppBuilder where it was incorrectly looking for {ProjectName}.runtimeconfig.json instead of the actual generated file {AssemblyName}.runtimeconfig.json, causing test failures. The solution switches to using the standardized runtimeconfig.bin binary format for runtime configuration lookup.

Key Changes:

• Modified ParseRuntimeConfigProperties method to read from runtimeconfig.bin instead of guessing JSON filenames
• Implemented binary format parsing using BlobReader from System.Reflection.Metadata
• Added unsafe code support to enable direct memory access for efficient binary reading

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/tasks/AndroidAppBuilder/ApkBuilder.cs	Replaced JSON-based runtime config parsing with binary format reading using BlobReader
src/tasks/AndroidAppBuilder/AndroidAppBuilder.csproj	Added AllowUnsafeBlocks property to enable unsafe code for binary reading
src/tasks/TestExclusionListTasks/TestExclusionListTasks.csproj	Added AllowUnsafeBlocks property (appears unrelated to main changes)

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