Add CLOEXEC and NONBLOCK to pipe2 (#99) #27

Job	Run time
build / build_cxx_sysroot (-exnref-ehpic)	3m 43s
build / build_cxx_sysroot (-ehpic)	3m 9s
build / build_cxx_sysroot (-exnref-eh)	3m 24s
build / build_cxx_sysroot	3m 50s
build / build_cxx_sysroot (-eh)	3m 12s
release	21s
	17m 39s

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