[Xamarin.Android.Build.Tasks] avoid File.Exists() check

[jonathanpeppers]

dotnet-trace output of a dotnet new maui app:

dotnet trace collect --format speedscope -- C:\src\xamarin-android\bin\Release\dotnet\dotnet.exe build -bl --no-restore bar.csproj

Shows an interesting case of File.Exists():

49.88ms xamarin.android.build.tasks!Xamarin.Android.Tasks.FilterAssemblies.RunTask()
 8.09ms System.Private.CoreLib.il!System.IO.File.Exists(class System.String)

The common case is the files always exist. The rare case appears to be 783ac9e, which would be when something like a <ProjectReference/> doesn't exist.

Instead of calling File.Exists() on every .NET assembly (likely done multiple times in a build), we can handle FileNotFoundException and take appropriate action.

This will save ~8ms on every build, and we should get the exact same behavior as before. Potentially larger projects could even save more.

[dellis1972]

@jonathanpeppers I suspect the DeduplicateAssemblies method in ProcessAssemblies can use the same treatment. It would also help use remove some Linq usage

xamarin-android/src/Xamarin.Android.Build.Tasks/Tasks/ProcessAssemblies.cs

Line 121 in ee43220

void DeduplicateAssemblies (List<ITaskItem> output, Dictionary<string, ITaskItem> symbols)

[jonathanpeppers]

Yeah <ProcessAssemblies/> might be worth looking at later. It has a faster code path when there is 1 RID, which should be the case for Debug builds:

xamarin-android/src/Xamarin.Android.Build.Tasks/Tasks/ProcessAssemblies.cs

Lines 55 to 62 in 2a16828

	// We only need to "dedup" assemblies when there is more than one RID
	if (RuntimeIdentifiers.Length > 1) {
	Log.LogDebugMessage ("Deduplicating assemblies per RuntimeIdentifier");
	DeduplicateAssemblies (output, symbols);
	} else {
	Log.LogDebugMessage ("Found a single RuntimeIdentifier");
	SetMetadataForAssemblies (output, symbols);
	}

So that might be why I didn't see this one.

[jonathanpeppers]

Ok, I need to handle DirectoryNotFoundException as well.