clang

Initial support for compile-time graph #481

Job	Run time
linux-x64-clang	7m 5s
linux-x64-clang-index	4m 34s
linux-x64-clang-generic-ndarray	11m 41s
linux-x64-clang-constexpr-eval	4m 19s
linux-x64-clang-constexpr-generic-ndarray-eval	6m 17s
linux-x64-clang-constexpr-no-stl-generic-ndarray-eval	5m 39s
linux-x64-clang-generic-ndarray-eval	7m 33s
linux-x64-clang-index	1m 54s
linux-x64-clang-no-stl	4m 53s
linux-x64-clang-no-stl-generic-ndarray	9m 50s
linux-x64-clang-no-stl-generic-ndarray-eval	6m 19s
	1h 10m 4s

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