Avoid calling TestLib::perl2host on a symlinked directory

Certain versions of msys2/Windows have been observed to resolve symlinks
in perl2host rather than just follow them. This defeats using a
symlinked shorter path to a longer path, and makes certain tests fail.
We therefore call perl2host on the parent directory of the symlink and
thereafter just use that result.

Apply to release 14 where the problem has been observed.

src/bin/pg_basebackup/t/010_pg_basebackup.pl

@@ -238,11 +238,13 @@ $node->start;
 # to our physical temp location.  That way we can use shorter names
 # for the tablespace directories, which hopefully won't run afoul of
 # the 99 character length limit.
-my $shorter_tempdir = TestLib::tempdir_short . "/tempdir";
+my $sys_tempdir = TestLib::tempdir_short;
+my $real_sys_tempdir = TestLib::perl2host($sys_tempdir) . "/tempdir";
+my $shorter_tempdir =  $sys_tempdir . "/tempdir";
 dir_symlink "$tempdir", $shorter_tempdir;
 
 mkdir "$tempdir/tblspc1";
-my $realTsDir    = TestLib::perl2host("$shorter_tempdir/tblspc1");
+my $realTsDir    = "$real_sys_tempdir/tblspc1";
 my $real_tempdir = TestLib::perl2host($tempdir);
 $node->safe_psql('postgres',
 	"CREATE TABLESPACE tblspc1 LOCATION '$realTsDir';");
@@ -275,7 +277,7 @@ SKIP:
 
 	# Recover tablespace into a new directory (not where it was!)
 	my $repTsDir     = "$tempdir/tblspc1replica";
-	my $realRepTsDir = TestLib::perl2host("$shorter_tempdir/tblspc1replica");
+	my $realRepTsDir = "$real_sys_tempdir/tblspc1replica";
 	mkdir $repTsDir;
 	TestLib::system_or_bail($tar, 'xf', $tblspc_tars[0], '-C', $repTsDir);
 
@@ -390,7 +392,7 @@ ok( -d "$tempdir/backup1/pg_replslot",
 rmtree("$tempdir/backup1");
 
 mkdir "$tempdir/tbl=spc2";
-$realTsDir = TestLib::perl2host("$shorter_tempdir/tbl=spc2");
+$realTsDir = "$real_sys_tempdir/tbl=spc2";
 $node->safe_psql('postgres', "DROP TABLE test1;");
 $node->safe_psql('postgres', "DROP TABLE tblspc1_unlogged;");
 $node->safe_psql('postgres', "DROP TABLESPACE tblspc1;");
@@ -409,7 +411,7 @@ $node->safe_psql('postgres', "DROP TABLESPACE tblspc2;");
 rmtree("$tempdir/backup3");
 
 mkdir "$tempdir/$superlongname";
-$realTsDir = TestLib::perl2host("$shorter_tempdir/$superlongname");
+$realTsDir = "$real_sys_tempdir/$superlongname";
 $node->safe_psql('postgres',
 	"CREATE TABLESPACE tblspc3 LOCATION '$realTsDir';");
 $node->command_ok([ 'pg_basebackup', '-D', "$tempdir/tarbackup_l3", '-Ft' ],