Avoid gcc 11 strncpy warning

[jasondrogba]

reference: libfuse#447
running make -j8 have warning:

In file included from /usr/include/string.h:535,
                 from fuse.c:23:
In function 'strncpy',
    inlined from 'add_name' at fuse.c:908:2:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:95:10: warning: '__builtin_strncpy' output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
   95 |   return __builtin___strncpy_chk (__dest, __src, __len,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   96 |                                   __glibc_objsize (__dest));
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~
fuse.c: In function 'add_name':
fuse.c:884:22: note: length computed here
  884 |         size_t len = strlen(name);
      |                      ^~~~~~~~~~~~
In file included from /usr/include/string.h:535,
                 from fuse_lowlevel.c:22:
In function 'strncpy',
    inlined from 'fuse_add_dirent' at fuse_lowlevel.c:263:2:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:95:10: warning: '__builtin_strncpy' output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
   95 |   return __builtin___strncpy_chk (__dest, __src, __len,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   96 |                                   __glibc_objsize (__dest));
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~
fuse_lowlevel.c: In function 'fuse_add_dirent':
fuse_lowlevel.c:253:28: note: length computed here
  253 |         unsigned namelen = strlen(name);
      |                            ^~~~~~~~~~~~
  CC       mount_util.lo
  CC       ulockmgr.lo