[llvm] [SYCL] Add libsycl, a SYCL RT library implementation project (PR #144372)

[Alexey Bader via llvm-commits]

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@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file is a SYCL2020 standard header file.
----------------
bader wrote:

```suggestion
/// This file is a SYCL 2020 standard header file.
```

https://github.com/llvm/llvm-project/pull/144372