6.7 changed the names of the time members in struct inode, so we can't
assign back to it because we don't know its name. In practice this
doesn't matter though - if we're missing current_time(), then we must be
on <4.9, and we know our fallback will need to return timespec.
Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Rob Norris <robn@despairlabs.com> Sponsored-by: https://github.com/sponsors/robn
Closes #15681