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 <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #16636 
Closes #16640

config/user.m4

@@ -33,7 +33,7 @@ AC_DEFUN([ZFS_AC_CONFIG_USER], [
 	ZFS_AC_CONFIG_USER_MAKEDEV_IN_MKDEV
 	ZFS_AC_CONFIG_USER_ZFSEXEC
 
-	AC_CHECK_FUNCS([execvpe issetugid mlockall strlcat strlcpy gettid])
+	AC_CHECK_FUNCS([execvpe issetugid mlockall strerror_l strlcat strlcpy gettid])
 
 	AC_SUBST(RM)
 ])

include/libzutil.h

@@ -276,7 +276,11 @@ _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