test: do not open fixture files for writing
Use temp directory for open with O_DSYNC
(which indicates a write may
occur) rather than fixtures
directory. Additionally, test can be run
on macOS so allow that in addition to Linux.
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
commit message follows commit guidelines
Affected core subsystem(s)
test fs