perf build-id: Fix off-by-one bug when printing kernel/module build-id

perf build-id: Fix off-by-one bug when printing kernel/module build-id

When changing sprintf functions to snprintf, one byte got lost. Since
snprintf ones do not handle the '\0' terminating character, the number
of printed characters is 40, while sizeof(sbuild_id) is 41, including
the terminating '\0' character.

This makes the later check fail so that nothing is printed.

Fix that.

Before:

    [Michael@Carbon ~]$ perf buildid-list -k
    [Michael@Carbon ~]$

After:

    [Michael@Carbon ~]$ perf buildid-list -k
    a527806324d543c4bc3ff2f9c9519d494fed5f68
    [Michael@Carbon ~]$

Fixes: fccaaf6fbbc59910 ("perf build-id: Change sprintf functions to snprintf")
Signed-off-by: Michael Petlan <mpetlan@redhat.com>
Tested-by: Ian Rogers <irogers@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>