Fallback to strerror() when strerror_l() isn't available

Some C libraries, such as uClibc, do not provide strerror_l() in
which case we fallback to strerror().

Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #16636 
Closes #16640

include/libzutil.h

@@ -274,7 +274,11 @@ _LIBZUTIL_H void update_vdev_config_dev_sysfs_path(nvlist_t *nv,
  * Thread-safe strerror() for use in ZFS libraries
  */
 static inline char *zfs_strerror(int errnum) {
+#ifdef HAVE_STRERROR_L
 	return (strerror_l(errnum, uselocale(0)));
+#else
+	return (strerror(errnum));
+#endif
 }
 
 #ifdef	__cplusplus