fallocate fails because it is not in any promise group

`__NR_fallocate` isn't used anywhere.

Should it be in [`kPledgeStdio[]`](https://github.com/jart/pledge/blob/8693ebe15a30bd4235165ad72a469da29ca067cf/libc/calls/pledge-linux.c#L547)?

Currently gives `EPERM`:

```
fallocate(3, 0, 0, 10485760) = -1 EPERM (Operation not permitted)
```

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Is / should there be a CLI flag that allows me to give individual syscalls directly, to handle cases like this?

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Also, would it make sense to have some test that checks that each syscall is in some promise group?

Start in libc/calls/pledge-linux.c around kPledgeStdio[] and trace how __NR_fallocate is assigned to promise groups. Check the existing syscall-related tests or test entry points, then verify that fallocate no longer returns EPERM under the appropriate promise and that any proposed syscall-coverage check has a clear passing condition.

Written by the indexing model from the issue text.