cmd/cue: export cannot write to a named pipe using --outfile

[jpluscplusm]

What version of CUE are you using (cue version)?

$ cue version
cue version v0.11.0

go version go1.23.3
      -buildmode exe
       -compiler gc
       -trimpath true
     CGO_ENABLED 0
          GOARCH amd64
            GOOS linux
         GOAMD64 v1
cue.lang.version v0.11.0

Does this issue reproduce with the latest stable release?

I suspect so; v0.11.1 doesn't appear to contain any changes in this area.

What did you do?

exec mkfifo aPipe
exec cat aPipe &
exec cue export file.cue --outfile=aPipe --out json
-- file.cue --
x: 1

What did you expect to see?

A passing testscript.

What did you see instead?

> exec mkfifo aPipe
> exec cat aPipe &
> exec cue export file.cue --outfile=aPipe --out json
[stderr]
error writing "aPipe": file already exists
[exit status 1]
FAIL: /tmp/testscript1911196150/fifo.txtar/script.txtar:3: unexpected command failure
[background] cat aPipe: signal: interrupt