feat: reboot(2) for OpenBSD/NetBSD #437

Job	Run time
linux_native_builds (x86_64-unknown-linux-gnu)	1m 29s
tier3 (x86_64-unknown-dragonfly)	59s
linux_native_builds (x86_64-unknown-linux-musl)	1m 17s
tier3 (x86_64-unknown-openbsd)	1m 2s
minver	16s
macos	1m 50s
tier3 (x86_64-unknown-haiku)	59s
rust_stable	1m 10s
tier3 (i686-unknown-hurd-gnu)	54s
rustfmt	17s
redox	43s
cross_compiling (aarch64-linux-android)	36s
cross (arm-unknown-linux-gnueabi)	1m 37s
cross_compiling (arm-linux-androideabi)	36s
cross (armv7-unknown-linux-gnueabihf)	1m 37s
cross_compiling (armv7-linux-androideabi)	38s
cross (i686-unknown-linux-gnu)	1m 48s
cross_compiling (i686-linux-android)	36s
cross (i686-unknown-linux-musl)	1m 50s
cross_compiling (x86_64-linux-android)	38s
cross (mips-unknown-linux-gnu)	1m 44s
cross_compiling (arm-unknown-linux-musleabi)	36s
cross (mips64-unknown-linux-gnuabi64)	1m 40s
cross_compiling (x86_64-unknown-fuchsia)	30s
cross (mips64el-unknown-linux-gnuabi64)	1m 41s
cross_compiling (x86_64-unknown-illumos)	33s
cross (mipsel-unknown-linux-gnu)	1m 41s
cross_compiling (aarch64-apple-ios, true)	32s
cross (powerpc64le-unknown-linux-gnu)	1m 46s
cross_compiling (powerpc64-unknown-linux-gnu)	39s
cross_compiling (s390x-unknown-linux-gnu)	39s
cross_compiling (x86_64-unknown-linux-gnux32)	38s
cross_compiling (x86_64-unknown-netbsd)	31s
	34m 2s

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