Does not build on WebAssembly WASI due to lack of `dup`, `dup2`, and `pipe` system calls

[whitequark]

These are not available architecturally.

[whitequark]

Thanks, that was very fast!

[whitequark]

@vitaut Do you have an idea of when this commit would appear in a release? I'd like to have my port of Slang to WASI merged, but the maintainer requests that I not use a git hash for the {fmt} version.

[vitaut]

I don't have a specific date but I plan to start putting together a new release once #3675 is done and the currently in-flight PRs are merged.

Note that FMT_USE_FCNTL can be set by users so you probably don't need to wait for a new release, just set it in the build config and it will work with any {fmt} version.

[whitequark]

Thanks, that works!