tools check_headers.sh: Add check variant that excludes some hunks

tools check_headers.sh: Add check variant that excludes some hunks

With 6d74e1e371d43a7b ("tools/lib/list_sort: remove redundant code for
cond_resched handling") we end up with a multi-line variation in the
merge_final() implementation, one that the simple line based exceptions
we had so far can't cope.

Thus this check has been failing:

  Warning: Kernel ABI header differences:
    diff -u tools/lib/list_sort.c lib/list_sort.c

So add a new check routine that uses grep -vf to exclude some hunks that
we store in the tools/perf/check-header_ignore_hunks/ directory.

This first patch is just the new check routine, the next one will use it
to check lib/list_sort.c.

Acked-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Link: https://lore.kernel.org/lkml/20240930202136.16904-2-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>