sbin/hammer: Fix compile warning on Linux
Warned by gcc 7.3.1 in Fedora.
Extend the size of destination string.
dirent::d_name[] is 256 bytes in Linux (and *BSD).
--
cmd_abort.c: In function 'hammer_cmd_abort_cleanup':
cmd_abort.c:73:44: warning: '%s' directive output may be truncated writing up to 255 bytes into a region of size 55 [-Wformat-truncation=]
snprintf (pidfile, PIDFILE_BUFSIZE, "%s/%s",
^~
cmd_abort.c:73:4: note: 'snprintf' output between 10 and 265 bytes into a destination of size 64
snprintf (pidfile, PIDFILE_BUFSIZE, "%s/%s",
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pidfile_loc, den->d_name);
~~~~~~~~~~~~~~~~~~~~~~~~~