Add some copyright headers

src/core-sdk-tasks/CollatePackageDownloads.cs

@@ -1,4 +1,7 @@
-using System;
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;

src/core-sdk-tasks/GenerateSdkRuntimeIdentifierChain.cs

@@ -1,4 +1,7 @@
-using System;
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;

src/core-sdk-tasks/GetLinuxNativeInstallerDependencyVersions.cs

@@ -1,4 +1,7 @@
-using System;
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;

src/core-sdk-tasks/GetRuntimePackRids.cs

@@ -1,4 +1,7 @@
-using System;
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;

src/core-sdk-tasks/JsonPropertyParser.cs

@@ -1,3 +1,6 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
 using System;
 using System.IO;
 using Microsoft.Build.Framework;