Compile timespec for net feature

[HalFrgrd]

Fixes the problem found here #1655 (comment)

[ogoffart]

Thanks for the PR

@sunfishcode would be nice to have a release, because rustix 1.1.5 is failling to compile on our android CI

[darkhonor]

This is the right fix, and it predates the duplicate I opened in #1690, which I have closed in favour of this one.

Offering one thing from it in case it is useful here rather than as a separate PR. The check_no_default_features job already checks time and time,use-libc individually, and the same pair for net would have caught this:

    - run: cargo check --workspace --release --no-default-features --features net -vv
    - run: cargo check --workspace --release --no-default-features --features net,use-libc -vv

Verified against v1.1.5 on rustc 1.98.1 with the job's own RUSTFLAGS: -D warnings -D elided-lifetimes-in-paths: net fails with six E0433s through the linux_raw backend and net,use-libc with three through libc, and both pass with the one-line change in this PR. Entirely your call whether it belongs here or not at all.

Context on the impact, since a release is already being asked for above: this also breaks consumers that set default-features = false to opt into a minimal API surface. Full repro and verification matrix are in #1689, which I am closing as a duplicate of this.