sysdeps/managarm: push/pop rax in crt[in].o #3254

Job	Run time
Compile sysdeps (dripos)	2m 10s
Compile sysdeps (lemon)	43s
Build mlibc (x86_64, mlibc)	3m 48s
Build mlibc (x86_64, mlibc-static)	2m 56s
Compile sysdeps (aero)	3m 29s
Build mlibc (x86_64, mlibc-shared)	4m 3s
Compile sysdeps (ironclad)	2m 22s
Build mlibc (x86_64, mlibc-ansi-only)	2m 59s
Compile sysdeps (lyre)	44s
Build mlibc (x86_64, mlibc-headers-only)	1m 46s
Compile sysdeps (keyronex)	2m 22s
Build mlibc (riscv64, mlibc)	3m 55s
Build mlibc (riscv64, mlibc-static)	4m 48s
Build mlibc (riscv64, mlibc-shared)	3m 7s
Build mlibc (riscv64, mlibc-ansi-only)	2m 59s
Build mlibc (riscv64, mlibc-headers-only)	1m 48s
Build mlibc (aarch64, mlibc)	3m 50s
Build mlibc (aarch64, mlibc-static)	3m 13s
Build mlibc (aarch64, mlibc-shared)	3m 4s
Build mlibc (aarch64, mlibc-ansi-only)	2m 55s
Build mlibc (aarch64, mlibc-headers-only)	1m 45s
	58m 46s

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