sysdeps/managarm: Implement sys_reboot #997

Job	Run time
Compile sysdeps (dripos)	2m 22s
Build mlibc (x86_64, mlibc, gcc)	4m 2s
Compile sysdeps (lemon)	2m 23s
Build mlibc (x86_64, mlibc-static, gcc)	3m 19s
Compile sysdeps (aero)	2m 22s
Build mlibc (x86_64, mlibc-shared, gcc)	3m 13s
Compile sysdeps (ironclad)	2m 19s
Build mlibc (x86_64, mlibc-ansi-only, gcc)	3m 7s
Compile sysdeps (lyre)	2m 22s
Build mlibc (x86_64, mlibc-headers-only, gcc)	2m 8s
Compile sysdeps (keyronex)	2m 23s
Compile sysdeps (managarm)	2m 15s
Build mlibc (riscv64, mlibc, gcc)	3m 49s
Compile sysdeps (vinix)	2m 19s
Build mlibc (riscv64, mlibc-static, gcc)	4m 41s
Build mlibc (riscv64, mlibc-shared, gcc)	3m 20s
Build mlibc (riscv64, mlibc-ansi-only, gcc)	3m 5s
Build mlibc (riscv64, mlibc-headers-only, gcc)	2m 16s
Build mlibc (aarch64, mlibc, gcc)	4m 13s
Build mlibc (aarch64, mlibc-static, gcc)	3m 31s
Build mlibc (aarch64, mlibc-shared, gcc)	3m 42s
Build mlibc (aarch64, mlibc-ansi-only, gcc)	3m 26s
Build mlibc (aarch64, mlibc-headers-only, gcc)	2m 20s
Build mlibc (x86, mlibc, gcc)	4m 8s
Build mlibc (x86, mlibc-static, gcc)	3m 25s
Build mlibc (x86, mlibc-shared, gcc)	3m 28s
Build mlibc (x86, mlibc-ansi-only, gcc)	3m 14s
Build mlibc (x86, mlibc-headers-only, gcc)	2m 14s
Build mlibc (x86_64, mlibc, clang)	3m 34s
	1h 29m 0s

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