Fix the following strncpy() string truncation warning:
In function ‘strncat’,
inlined from ‘print_cgroup’ at lscgroup.c:149:4:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:136:10: warning: ‘__builtin___strncat_chk’ output
may be truncated copying between 0 and 4095 bytes from a string of length 4095 [-Wstringop-truncation]
136 | return __builtin___strncat_chk (__dest, __src, __len, __bos (__dest));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>