Avoid hardcoded illink.tasks TFM

Replaces #109619

We made a similar change recently in arcade to not use the TFM but a normalized value of the TargetFrameworkIdentifier property for tools packages.

Author: ViktorHofer

eng/packaging.targets

@@ -303,13 +303,21 @@
 
   <!-- Manual invoked target that can be used by toolset packages by adding it to the `TargetsForTfmSpecificContentInPackage` property. -->
   <Target Name="AddBuildOutputToToolsPackage">
+    <PropertyGroup Condition="'$(BuildTaskTargetTfmSpecificFolder)' == ''">
+      <BuildTaskTargetTfmSpecificFolder Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp'">net</BuildTaskTargetTfmSpecificFolder>
+      <BuildTaskTargetTfmSpecificFolder Condition="'$(TargetFrameworkIdentifier)' == '.NETFramework'">netframework</BuildTaskTargetTfmSpecificFolder>
+    </PropertyGroup>
+
+    <Error Text="The 'BuildTaskTargetTfmSpecificFolder' property must be explicitly set when not targeting .NETCoreApp or .NETFramework"
+           Condition="'$(BuildTaskTargetTfmSpecificFolder)' == ''" />
+
     <ItemGroup>
       <!-- Include build outputs in the package under tools directory. -->
       <_BuildOutputPackageFile Include="$(OutputPath)**"
                                Exclude="$(OutputPath)publish\**;
                                         $(OutputPath)" />
       <TfmSpecificPackageFile Include="@(_BuildOutputPackageFile)"
-                              PackagePath="tools/$(TargetFramework)/%(RecursiveDir)%(FileName)%(Extension)" />
+                              PackagePath="tools/$(BuildTaskTargetTfmSpecificFolder)/%(RecursiveDir)%(FileName)%(Extension)" />
       <TfmSpecificDebugSymbolsFile Include="@(TfmSpecificPackageFile->WithMetadataValue('Extension', '.pdb'))"
                                    TargetPath="/%(TfmSpecificPackageFile.PackagePath)/%(Filename)%(Extension)"
                                    TargetFramework="$(TargetFramework)"

src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.Tasks.props

@@ -18,8 +18,8 @@ Copyright (c) .NET Foundation. All rights reserved.
     <!-- Older SDKs used this property as a sentinel instead, to control the import of this file
          (but not the targets, which were included with the SDK). -->
     <UsingILLinkTasksSdk>true</UsingILLinkTasksSdk>
-    <ILLinkTasksAssembly Condition="'$(MSBuildRuntimeType)' == 'Core'">$(MSBuildThisFileDirectory)..\tools\net9.0\ILLink.Tasks.dll</ILLinkTasksAssembly>
-    <ILLinkTasksAssembly Condition="'$(MSBuildRuntimeType)' != 'Core'">$(MSBuildThisFileDirectory)..\tools\net472\ILLink.Tasks.dll</ILLinkTasksAssembly>
+    <ILLinkTasksAssembly Condition="'$(MSBuildRuntimeType)' == 'Core'">$(MSBuildThisFileDirectory)..\tools\net\ILLink.Tasks.dll</ILLinkTasksAssembly>
+    <ILLinkTasksAssembly Condition="'$(MSBuildRuntimeType)' != 'Core'">$(MSBuildThisFileDirectory)..\tools\netframework\ILLink.Tasks.dll</ILLinkTasksAssembly>
 
     <ILLinkAnalyzersPropsPath Condition="'$(ILLinkAnalyzersPropsPath)' == ''">$(MSBuildThisFileDirectory)Microsoft.NET.ILLink.Analyzers.props</ILLinkAnalyzersPropsPath>
   </PropertyGroup>