[Perl] Fix testsuite to work without . in @INC

"." was removed from @INC in Perl 5.26 for security reasons, and has
also been removed from older versions in some distros.

Fixes https://github.com/swig/swig/issues/997 reported by lfam.

Examples/test-suite/perl5/run-perl-test.pl

@@ -7,7 +7,7 @@ use strict;
 
 my $command = shift @ARGV;
 
-my $output = `$^X $command 2>&1`;
+my $output = `$^X -I. $command 2>&1`;
 
 die "SWIG Perl test failed: \n\n$output\n"
   if $?;