Linux 6.8 compat: implement strlcpy fallback
Linux has removed strlcpy in favour of strscpy. This implements a
fallback implementation of strlcpy for this case.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Sponsored-by: https://despairlabs.com/sponsor/
Closes #15805
(cherry picked from commit 7466e09a492b644d39d85dd173e0f8051858a2a5)