Bug#47526 unit.pl fails to execute binaries when using Test::Harness 3.10

- Rewrite unit.pl so it prefers to use TAP::Harness directly.
  - Also add support for --verbose --noverbose

unittest/unit.pl

@@ -14,8 +14,8 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
-use Test::Harness qw(&runtests $verbose);
 use File::Find;
+use Getopt::Long;
 
 use strict;
 
@@ -35,6 +35,11 @@ unit - Run unit tests in directory
 
 =cut
 
+my $opt_verbose;
+GetOptions (
+  "verbose!"    => \$opt_verbose,
+) or die "Failed to parse options!: $!";
+
 my $cmd = shift;
 
 if (defined $cmd && exists $dispatch{$cmd}) {
@@ -51,6 +56,21 @@ Run all unit tests in the current directory and all subdirectories.
 =cut
 
 
+BEGIN {
+  # Test::Harness have been extensively rewritten in newer perl
+  # versions and is now just a backward compatibility wrapper
+  # (with a bug causing the HARNESS_PERL_SWITCHES to be mangled)
+  # Prefer to use TAP::Harness directly if available
+  if (eval "use TAP::Harness; 1") {
+    eval 'sub NEW_HARNESS { 1 }';
+    warn "using TAP::Harness";
+  } else {
+    eval "use Test::Harness; 1" or  die "couldn't find Test::Harness!";
+    eval 'sub NEW_HARNESS { 0 }';
+  }
+}
+
+
 sub _find_test_files (@) {
     my @dirs = @_;
     my @files;
@@ -92,8 +112,19 @@ sub run_cmd (@) {
     if (@files > 0) {
         # Removing the first './' from the file names
         foreach (@files) { s!^\./!! }
-        $ENV{'HARNESS_PERL_SWITCHES'} .= q" -e 'exec @ARGV'";
-        runtests @files;
+
+        if (NEW_HARNESS())
+        {
+          my %args = ( exec => [ ], verbosity => $opt_verbose );
+          my $harness = TAP::Harness->new( \%args );
+          $harness->runtests(@files);
+        }
+        else
+        {
+          $ENV{'HARNESS_VERBOSE'} =  $opt_verbose;
+          $ENV{'HARNESS_PERL_SWITCHES'} .= ' -e "exec @ARGV"';
+          runtests(@files);
+        }
     }
 }