Fix helpers module path lookup on newer Perl versions.

tools/buildbot/bootstrap.pl

@@ -9,6 +9,8 @@ use File::Path;
 my ($myself, $path) = fileparse($0);
 chdir($path);
 
+use FindBin;
+use lib $FindBin::Bin;
 require 'helpers.pm';
 
 #Go back to tree root.

tools/buildbot/package.pl

@@ -29,6 +29,8 @@ chomp $ftp_path;
 my ($myself, $path) = fileparse($0);
 chdir($path);
 
+use FindBin;
+use lib $FindBin::Bin;
 require 'helpers.pm';
 
 #Switch to the output folder.

tools/buildbot/startbuild.pl

@@ -6,6 +6,8 @@ use File::Basename;
 my ($myself, $path) = fileparse($0);
 chdir($path);
 
+use FindBin;
+use lib $FindBin::Bin;
 require 'helpers.pm';
 
 chdir('../../../OUTPUT');

tools/buildbot/symstore.pl

@@ -5,6 +5,8 @@ use File::Basename;
 my ($myself, $path) = fileparse($0);
 chdir($path);
 
+use FindBin;
+use lib $FindBin::Bin;
 require 'helpers.pm';
 
 chdir('..');