core: fix build when seccomp is off

[KanjiMonster]

Something went wrong when 6aa2c55 was cherry-picked for v250-stable, causing it to fail to build when seccomp is disabled.

Fix this by changing the code to how it looks like in other versions of the backported commit, slightly adapted to the file's style in v250.

Fixes the following build error:

| ../git/src/core/main.c: In function 'parse_config_file': | ../git/src/core/main.c:721:101: error: lvalue required as unary '&' operand
|   721 |                 { "Manager", "SystemCallArchitectures",      config_parse_syscall_archs,         0, &DISABLED_CONFIGURATION                },
|       |                                                                                                     ^

Fixes: 8e8c7d5 ("pid1: generate compat warning for SystemCallArchitectures= if seccomp is off")

[KanjiMonster]

No idea if v250 is even still maintained (or "maintained"), couldn't find any information about that, so feel free to close if it's EOL. Just didn't want to keep the fix to myself.

[packit-as-a-service]

We were not able to find or create Copr project packit/systemd-systemd-stable-444 specified in the config with the following error:

Cannot create a new Copr project (owner=packit project=systemd-systemd-stable-444 chroots=[]): chroots: '[]' is not a valid choice for this field.. Copr HTTP response is 400 BAD REQUEST.

---

Unless the HTTP status code above is >= 500, please check your configuration for:

1. typos in owner and project name (groups need to be prefixed with @)
2. whether the project name doesn't contain not allowed characters (only letters, digits, underscores, dashes and dots must be used)
3. whether the project itself exists (Packit creates projects only in its own namespace)
4. whether Packit is allowed to build in your Copr project
5. whether your Copr project/group is not private

[bluca]

This branch is no longer maintained. That said, might as well merge it given it's obviously correct.