sysdeps/managarm: Add sys_fstatfs #4216

Job	Run time
Build mlibc (x86_64, mlibc, gcc)	3m 51s
Compile sysdeps (dripos)	2m 18s
Build mlibc (x86_64, mlibc-static, gcc)	3m 40s
Compile sysdeps (lemon)	2m 17s
Build mlibc (x86_64, mlibc-shared, gcc)	3m 6s
Compile sysdeps (aero)	2m 18s
Build mlibc (x86_64, mlibc-ansi-only, gcc)	2m 57s
Compile sysdeps (ironclad)	2m 18s
Build mlibc (x86_64, mlibc-headers-only, gcc)	1m 59s
Compile sysdeps (lyre)	2m 17s
Build mlibc (riscv64, mlibc, gcc)	3m 48s
Compile sysdeps (keyronex)	2m 18s
Build mlibc (riscv64, mlibc-static, gcc)	4m 31s
Compile sysdeps (managarm)	2m 14s
Build mlibc (riscv64, mlibc-shared, gcc)	3m 7s
Compile sysdeps (vinix)	2m 19s
Compile sysdeps (astral)	2m 19s
Build mlibc (riscv64, mlibc-ansi-only, gcc)	2m 55s
Build mlibc (riscv64, mlibc-headers-only, gcc)	1m 59s
Build mlibc (aarch64, mlibc, gcc)	4m 5s
Build mlibc (aarch64, mlibc-static, gcc)	3m 24s
Build mlibc (aarch64, mlibc-shared, gcc)	3m 20s
Build mlibc (aarch64, mlibc-ansi-only, gcc)	3m 29s
Build mlibc (aarch64, mlibc-headers-only, gcc)	2m 3s
Build mlibc (x86, mlibc, gcc)	3m 57s
Build mlibc (x86, mlibc-static, gcc)	3m 15s
Build mlibc (x86, mlibc-shared, gcc)	3m 13s
Build mlibc (x86, mlibc-ansi-only, gcc)	3m 3s
Build mlibc (x86, mlibc-headers-only, gcc)	2m 4s
Build mlibc (m68k, mlibc, gcc)	3m 39s
Build mlibc (m68k, mlibc-static, gcc)	3m 0s
Build mlibc (m68k, mlibc-shared, gcc)	2m 59s
Build mlibc (m68k, mlibc-ansi-only, gcc)	3m 14s
Build mlibc (m68k, mlibc-headers-only, gcc)	2m 32s
Build mlibc (x86_64, mlibc, clang)	3m 29s
	1h 43m 17s

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