clang

Add support for cuda & sycl mean #475

Job	Run time
linux-x64-clang	6m 43s
linux-x64-clang-constexpr-eval	4m 6s
linux-x64-clang-constexpr-no-stl-generic-ndarray-eval	5m 15s
linux-x64-clang-index	3m 12s
linux-x64-clang-generic-ndarray	11m 10s
linux-x64-clang-generic-ndarray-eval	7m 5s
linux-x64-clang-index	1m 48s
linux-x64-clang-no-stl	4m 56s
linux-x64-clang-no-stl-generic-ndarray	9m 4s
linux-x64-clang-no-stl-generic-ndarray-eval	6m 9s
linux-x64-clang-constexpr-generic-ndarray-eval	5m 58s
	1h 5m 26s

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