Add TaskFactory="TaskHostFactory" Runtime="NET" to xa-prep-tasks and BootstrapTasks UsingTask elements

[Copilot]

Windows file locking on task assembly DLLs causes build failures when MSBuild loads xa-prep-tasks and BootstrapTasks in-process. Running them out-of-process via TaskHostFactory avoids the lock, and Runtime="NET" ensures they run on .NET even under MSBuild.exe (.NET Framework) in Visual Studio.

Changes

• Added TaskFactory="TaskHostFactory" Runtime="NET" to all 42 <UsingTask/> elements referencing $(PrepTasksAssembly) or $(BootstrapTasksAssembly) across 16 files
• Not applied to shipped product <UsingTask/> elements (Xamarin.Android.Common.targets, Microsoft.Android.Sdk/*.targets, etc.) — these would affect customer builds
• Updated .github/copilot-instructions.md with guidance for future task additions

Example

Before:

<UsingTask AssemblyFile="$(BootstrapTasksAssembly)" TaskName="Xamarin.Android.Tools.BootstrapTasks.Adb" />

After:

<UsingTask AssemblyFile="$(BootstrapTasksAssembly)" TaskName="Xamarin.Android.Tools.BootstrapTasks.Adb" TaskFactory="TaskHostFactory" Runtime="NET" />

Reference: https://github.com/rainersigwald/build-task-in-solution-demo, UsingTask docs

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[Copilot]

Pull request overview

This PR adds TaskFactory="TaskHostFactory" Runtime="NET" attributes to all internal build-time <UsingTask/> elements that reference $(PrepTasksAssembly) (xa-prep-tasks) or $(BootstrapTasksAssembly), to run these tasks out-of-process and avoid Windows file locking issues when MSBuild loads the task assembly DLLs in-process.

Changes:

• Added TaskFactory="TaskHostFactory" Runtime="NET" to all 42 <UsingTask/> elements referencing internal build task assemblies across 16 target/project files
• Updated .github/copilot-instructions.md with guidance for future task additions, including a clear note to NOT apply this to shipped product UsingTask elements

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
.github/copilot-instructions.md	Added documentation for the TaskHostFactory convention on internal build tasks
build-tools/scripts/TestApks.targets	Updated 15 UsingTask elements (BootstrapTasks + PrepTasks)
build-tools/scripts/XAVersionInfo.targets	Updated 6 UsingTask elements (PrepTasks Git-related tasks)
build-tools/installers/create-installers.targets	Updated 1 UsingTask element (PrepTasks ReplaceFileContents)
build-tools/create-packs/Directory.Build.targets	Updated 1 UsingTask element (PrepTasks ReplaceFileContents)
build-tools/create-packs/Microsoft.NET.Sdk.Android.proj	Updated 1 UsingTask element (PrepTasks ReplaceFileContents)
build-tools/create-packs/Microsoft.Android.Sdk.proj	Updated 1 UsingTask element (BootstrapTasks GenerateUnixFilePermissions)
build-tools/create-android-api/create-android-api.csproj	Updated 1 UsingTask element (BootstrapTasks RunParallelCmds)
src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.targets	Updated 5 UsingTask elements (BootstrapTasks + PrepTasks)
src/Mono.Android/Mono.Android.targets	Updated 3 UsingTask elements (PrepTasks + BootstrapTasks)
src/Mono.Android.Runtime/Mono.Android.Runtime.csproj	Updated 1 UsingTask element (PrepTasks ReplaceFileContents)
src/aapt2/aapt2.targets	Updated 2 UsingTask elements (PrepTasks + BootstrapTasks)
src/bundletool/bundletool.targets	Updated 1 UsingTask element (PrepTasks DownloadUri)
src/native/native.targets	Updated 1 UsingTask element (BootstrapTasks RunParallelCmds)
src/native/common/libunwind/libunwind-xamarin.targets	Updated 1 UsingTask element (BootstrapTasks RunParallelCmds)
tests/api-compatibility/api-compatibility.targets	Updated 1 UsingTask element (BootstrapTasks Zip)
tests/CodeGen-Binding/.../Xamarin.Android.LibraryProjectZip-LibBinding.targets	Updated 1 UsingTask element (PrepTasks ReplaceFileContents)