[COMPILER REQUEST]: Enable libsycl for LLVM/Clang compilers

Compiler name

LLVM Clang

Compiler version

Clang trunk/assertions

Compiler language

C++

Compiler homepage

https://clang.llvm.org

Motivation

The LLVM/Clang implementation of the SYCL 2020 specification, libsycl, has reached the point where some basic SYCL programs can be compiled (and run on systems with a supported GPU). It would now be useful to use compiler-explorer.com for evaluation purposes and comparison with the SYCL implementation provided with the Intel ICX compiler. However, libsycl is not currently enabled by default, and is not enabled when building the compiler-explorer.com collection of compilers. As a result, inclusion of the <sycl/sycl.hpp> header file fails. See https://godbolt.org/z/bfq4553Wd.

libsycl is a small library, but does depend on liboffload, which is also a small library. Build support does not require a system with a GPU. Execution support is not requested at this time.

To enable libsycl and liboffload, add "offload" and "libsycl" to the LLVM_ENABLE_RUNTIMES CMake variable when configuring a LLVM/Clang build.