Avoid hard-coded perl path, check with env

Change-Id: If39a4991b487b14d21572d6e3d785df4c287f190
Reviewed-on: https://gerrit.libreoffice.org/22238Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>

bin/find-unusedheaders.pl

-#!/usr/bin/perl
+#!/usr/bin/env perl
 # This file is part of the LibreOffice project.
 #
 # This Source Code Form is subject to the terms of the Mozilla Public

bin/module-deps.pl

-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 use strict;
 use warnings;

oox/source/drawingml/customshapes/generatePresetsData.pl

-#!/usr/bin/perl
+#!/usr/bin/env perl
 #
 # This file is part of the LibreOffice project.
 #

oox/source/drawingml/customshapes/generatePresetsPPTXs.pl

-#!/usr/bin/perl
+#!/usr/bin/env perl
 #
 # This file is part of the LibreOffice project.
 #

sd/res/webview/webcast.pl

-#!/usr/bin/perl
+#!/usr/bin/env perl
 #
 # This file is part of the LibreOffice project.
 #

solenv/bin/fix-includes.pl

-#!/usr/bin/perl
+#!/usr/bin/env perl
 # This file is part of the LibreOffice project.
 #
 # This Source Code Form is subject to the terms of the Mozilla Public