The test only needs a unidirectional channel, and a pipe is sufficient
for that.
This may simplify things when running the test on Hurd; see
https://gitlab.gnome.org/GNOME/glib/-/issues/3148#note_1874198.
Additionally, set `O_NONBLOCK` on the pipe since the test seems to
expect that partial writes will succeed and that writes to a full buffer
will fail rather than block.
Signed-off-by: Philip Withnall <philip@tecnocode.co.uk>
Helps: #3148
Add SPDX license (but not copyright) headers to all files which follow a
certain pattern in their existing non-machine-readable header comment.
This commit was entirely generated using the command:
```
git ls-files gio/tests/*.c | xargs perl -0777 -pi -e 's/\n \*\n \* This library is free software; you can redistribute it and\/or\n \* modify it under the terms of the GNU Lesser General Public/\n \*\n \* SPDX-License-Identifier: LGPL-2.1-or-later\n \*\n \* This library is free software; you can redistribute it and\/or\n \* modify it under the terms of the GNU Lesser General Public/igs'
```
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Helps: #1415
