fix !unix builds

[babnskidata]

Fix "failed to resolve: use of undeclared type ErrorKind" error.

[jszwedko]

We just ran into this on Vector too: vectordotdev/vector#20955

The errors:

error[E0433]: failed to resolve: use of undeclared type `ErrorKind`
   --> C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\syslog-7.0.0\src/lib.rs:264:9
    |
264 |     Err(ErrorKind::UnsupportedPlatform)?
    |         ^^^^^^^^^ use of undeclared type `ErrorKind`
    |
help: consider importing this enum
    |
57  + use io::ErrorKind;
    |

error[E0433]: failed to resolve: use of undeclared type `ErrorKind`
   --> C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\syslog-7.0.0\src/lib.rs:275:9
    |
275 |     Err(ErrorKind::UnsupportedPlatform)?
    |         ^^^^^^^^^ use of undeclared type `ErrorKind`
    |
help: consider importing this enum
    |
57  + use io::ErrorKind;
    |

error[E0433]: failed to resolve: use of undeclared type `ErrorKind`
   --> C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\syslog-7.0.0\src/lib.rs:390:9
    |
390 |     Err(ErrorKind::UnsupportedPlatform)?
    |         ^^^^^^^^^ use of undeclared type `ErrorKind`
    |
help: consider importing this enum
    |
57  + use io::ErrorKind;
    |

error[E0433]: failed to resolve: use of undeclared type `ErrorKind`
   --> C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba[1500](https://github.com/vectordotdev/vector/actions/runs/10428621847/job/28885012430#step:6:1501)1f\syslog-7.0.0\src/lib.rs:422:9
    |
422 |     Err(ErrorKind::UnsupportedPlatform)?
    |         ^^^^^^^^^ use of undeclared type `ErrorKind`
    |
help: consider importing this enum
    |
57  + use io::ErrorKind;

[tisonkun]

FWIW I made a syslog library https://github.com/fast/fasyslog/ that implement similar functionality and guard the builds with CI.

[jszwedko]

Small bump on this @Geal . Do you think we could merge it to unblock upgrading to the latest version?