The seccomp test fails on aarch64 since commit
7720e84863377d5d1a2a20feb76d50df505ca680 because some syscalls are not
available.

This is because we check for all syscalls at once (for clarity
reasons) and are using #error if a syscall is not available. As #error doesn't
abort compilation, we get a "not declared in scope" error when using the
syscalls.

Instead, guard each syscall separate.

works on my AMD64 system as before. I don't own an arm64 system

to test the change.