disable package validation for .NET tools (#50941)

Author: baronfel

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.PackTool.targets

@@ -38,9 +38,14 @@ NOTE: This file is imported from the following contexts, so be aware when writin
             AssemblyFile="$(MicrosoftNETBuildTasksAssembly)" />
 
   <PropertyGroup>
-    <!-- tools are specially-formatted packages, so we tell nuget Pack to not even try to include build output -->
+    <!-- Tools are specially-formatted packages, so we tell nuget Pack to not even try to include build output.
+         Since this file is only loaded when PackAsTool is true, we can safely disable validation here. -->
     <IncludeBuildOutput>false</IncludeBuildOutput>
 
+    <!-- Tool packages are not library/API-providing packages, so they should not participate in API Compat validation at all.
+         Since this file is only loaded when PackAsTool is true, we can safely disable validation here. -->
+    <EnablePackageValidation>false</EnablePackageValidation>
+
     <!-- Determine information about all of the potential tool packages to build -->
     <!-- If shims are included, we need to make sure we restore for those RIDs so the apphost shims are available during restore/publish.
       This means that we need to set RuntimeIdentifiers. However we need to track certain information about the _users_ decisions around RIDs