build: fix TagName overflow issues

build: fix TagName overflow issues

The 'TagName' string is defined to be 40 characters in length, but
in three places we write into it with a format of "(%.39s)".  This
can result in a string of up to 42 characters, the 39 character user
string plus "()\0".  This overflows TagName, as we see in the new
complier warnings from gcc 7.2.1:

iogen.c:1277:6: note: 'sprintf' output between 3 and 42 bytes into a
destination of size 40
  sprintf( TagName, "(%.39s)", optarg );
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix this by limiting the user string to 37 characters.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>