Fix NativeAOT to use AndroidLinkMode=Full instead of SdkOnly

[Copilot]

NativeAOT was getting AndroidLinkMode=SdkOnly (BCL-only trimming) but TrimMode=full (aggressive trimming), creating a contradiction.

Changes

• Add explicit AndroidLinkMode=Full default for NativeAOT before existing fallback conditions
• Remove redundant '$(_AndroidRuntime)' == 'NativeAOT' check from TrimMode condition—now follows naturally from AndroidLinkMode=Full
• Fix indentation on adjacent line to match .editorconfig (spaces not tabs)

<!-- Before: NativeAOT fell through to SdkOnly via PublishTrimmed -->
<AndroidLinkMode Condition=" '$(AndroidLinkMode)' == '' and '$(PublishTrimmed)' == 'true' ">SdkOnly</AndroidLinkMode>
<TrimMode Condition=" '$(TrimMode)' == '' and ('$(AndroidLinkMode)' == 'Full' or '$(_AndroidRuntime)' == 'NativeAOT') ">full</TrimMode>

<!-- After: NativeAOT gets Full explicitly -->
<AndroidLinkMode Condition=" '$(AndroidLinkMode)' == '' and '$(_AndroidRuntime)' == 'NativeAOT' ">Full</AndroidLinkMode>
<AndroidLinkMode Condition=" '$(AndroidLinkMode)' == '' and '$(PublishTrimmed)' == 'true' ">SdkOnly</AndroidLinkMode>
<TrimMode Condition=" '$(TrimMode)' == '' and '$(AndroidLinkMode)' == 'Full' ">full</TrimMode>

Non-NativeAOT configurations (CoreCLR, MonoVM, Debug) remain unchanged.

Original prompt

Problem

In src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.DefaultProperties.targets, when using NativeAOT in Release configuration, AndroidLinkMode defaults to SdkOnly but TrimMode is forced to full. This is contradictory — SdkOnly implies only BCL/SDK assemblies are trimmed, but TrimMode=full aggressively trims all assemblies.

The relevant code (lines 104-111):

    <PublishTrimmed Condition=" '$(PublishTrimmed)' == '' and ('$(AndroidLinkMode)' == 'SdkOnly' or '$(AndroidLinkMode)' == 'Full') ">true</PublishTrimmed>
    <PublishTrimmed Condition=" '$(PublishTrimmed)' == '' and '$(Configuration)' == 'Release' and '$(AndroidLinkMode)' != 'None' ">true</PublishTrimmed>
    <AndroidLinkMode Condition=" '$(AndroidLinkMode)' == '' and '$(PublishTrimmed)' == 'true' ">SdkOnly</AndroidLinkMode>
    <AndroidLinkMode Condition=" '$(AndroidLinkMode)' == '' ">None</AndroidLinkMode>
    <!-- For compat with user code not marked trimmable, only trim opt-in by default. -->
    <TrimMode Condition=" '$(TrimMode)' == '' and ('$(AndroidLinkMode)' == 'Full' or '$(_AndroidRuntime)' == 'NativeAOT') ">full</TrimMode>
    <TrimMode Condition="'$(TrimMode)' == ''">partial</TrimMode>

Fix

1. Set AndroidLinkMode=Full by default for NativeAOT: Add a new default before the existing AndroidLinkMode fallback defaults (before line 106) so that NativeAOT gets Full instead of falling through to SdkOnly:

<AndroidLinkMode Condition=" '$(AndroidLinkMode)' == '' and '$(_AndroidRuntime)' == 'NativeAOT' ">Full</AndroidLinkMode>

This should go after the PublishTrimmed lines but before the existing AndroidLinkMode defaults on lines 106-107.

2. Remove the redundant '$(_AndroidRuntime)' == 'NativeAOT' check from the TrimMode condition on line 109: Since NativeAOT now gets AndroidLinkMode=Full, TrimMode=full will follow naturally from the AndroidLinkMode == 'Full' branch. Change line 109 from:

<TrimMode Condition=" '$(TrimMode)' == '' and ('$(AndroidLinkMode)' == 'Full' or '$(_AndroidRuntime)' == 'NativeAOT') ">full</TrimMode>

to:

<TrimMode Condition=" '$(TrimMode)' == '' and '$(AndroidLinkMode)' == 'Full' ">full</TrimMode>

The file to edit is: src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.DefaultProperties.targets

This pull request was created from Copilot chat.

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Pull request overview

Adjusts MSBuild default trimming/linking properties so NativeAOT builds don’t end up with conflicting defaults (AndroidLinkMode=SdkOnly vs TrimMode=full) in the .NET for Android SDK targets.

Changes:

• Default AndroidLinkMode to Full when $(_AndroidRuntime) is NativeAOT, ahead of existing fallback defaults.
• Simplify the TrimMode default condition to follow from AndroidLinkMode=Full (removing the redundant NativeAOT runtime check).
• Fix indentation on an adjacent line to match repository formatting.