FCNTL F_SETFL Ignore creation flags

[MousseARaser06]

This pull request aims at fixing #4352, it proceeds by having a list of platform-allowed flags (bits) for that operation (F_SETFL), and performing a bitwise AND assignment to exclude all of the flags that aren't allowed.
Allowed flags change from platform to platform

[rustbot]

Thank you for contributing to Miri! A reviewer will take a look at your PR, typically within a week or two.
Please remember to not force-push to the PR branch except when you need to rebase due to a conflict or when the reviewer asks you for it.

[RalfJung]

Thanks for the PR :)

We'll get to reviewing it eventually, but there are other PRs in the queue that will be reviewed first.

[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.