Msys2 tweaks for pg_validatebackup corruption test

1. Tell Msys2 not to mangle the tablespace map parameter
2. If rmdir doesn't work, fall back to trying unlink on the entry in
   pg_tblspc.

Discussion: https://postgr.es/m/7330a7c7-ce5f-9769-39a1-bdb0b32bb4a6@2ndQuadrant.com

src/bin/pg_validatebackup/t/003_corruption.pl

@@ -16,6 +16,9 @@ $master->start;
 # Include a user-defined tablespace in the hopes of detecting problems in that
 # area.
 my $source_ts_path = TestLib::perl2host(TestLib::tempdir_short());
+my $source_ts_prefix = $source_ts_path;
+$source_ts_prefix =~ s!(^[A-Z]:/[^/]*)/.*!$1!;
+
 $master->safe_psql('postgres', <<EOM);
 CREATE TABLE x1 (a int);
 INSERT INTO x1 VALUES (111);
@@ -105,6 +108,10 @@ for my $scenario (@scenario)
 		# Take a backup and check that it validates OK.
 		my $backup_path = $master->backup_dir . '/' . $name;
 		my $backup_ts_path = TestLib::perl2host(TestLib::tempdir_short());
+		# The tablespace map parameter confuses Msys2, which tries to mangle
+		# it. Tell it not to.
+		# See https://www.msys2.org/wiki/Porting/#filesystem-namespaces
+		local $ENV{MSYS2_ARG_CONV_EXCL} = $source_ts_prefix;
 		$master->command_ok(['pg_basebackup', '-D', $backup_path, '--no-sync',
 							'-T', "${source_ts_path}=${backup_ts_path}"],
 							"base backup ok");
@@ -179,7 +186,14 @@ sub mutilate_missing_tablespace
 	my $pathname = "$backup_path/pg_tblspc/$tsoid";
 	if ($windows_os)
 	{
-		rmdir($pathname) || die "$pathname: $!";
+		# rmdir works on some windows setups, unlink on others.
+		# Instead of trying to implement precise rules, just try one and then
+		# the other.
+		unless (rmdir($pathname))
+		{
+			my $err = $!;
+			unlink($pathname) || die "$pathname: rmdir: $err, unlink: $!";
+		}
 	}
 	else
 	{