MSVC: Remove any tmp_check directory before running a TAP test suite.

Back-patch to v11, where commit 90627cf9
made the GNU make build system do likewise.  Without this, when a
typical PostgresNode-using test failed, subsequent runs bailed out with
a "File exists" error.

src/tools/msvc/vcregress.pl

@@ -10,6 +10,7 @@ use Cwd;
 use File::Basename;
 use File::Copy;
 use File::Find ();
+use File::Path qw(rmtree);
 
 use Install qw(Install);
 
@@ -205,6 +206,7 @@ sub tap_check
 
 	$ENV{TESTDIR} = "$dir";
 
+	rmtree('tmp_check');
 	system(@args);
 	my $status = $? >> 8;
 	return $status;