Disable TAP tests of pg_receivewal for ZLIB on Windows

This reverts commit 91d395f, to avoid running those tests on Windows.
The tests are globally stable across all buildfarm members, except
fairywren (crash of pg_receivewal) and bowerdird (SIGBREAK preventing
the buildfarm run to complete).  Those errors are rather strange, as
other hosts with very similar characteristics are able to run those
tests without breaking a sweat.

For now, disable those tests on Windows to turn back the buildfarm to
green.

Per discussion with Andrew Dunstan.

Discussion: https://postgr.es/m/9040d5ed-6462-66a4-07ac-2923785ae563@dunslane.net

src/bin/pg_basebackup/t/020_pg_receivewal.pl

@@ -72,11 +72,13 @@ $primary->command_ok(
 my @partial_wals = glob "$stream_dir/*\.partial";
 is(scalar(@partial_wals), 1, "one partial WAL segment was created");
 
-# Check ZLIB compression if available.
+# Check ZLIB compression if available.  On Windows, some old versions
+# of zlib can cause some instabilities with this test, so disable it
+# for now.
 SKIP:
 {
-	skip "postgres was not built with ZLIB support", 5
-	  if (!check_pg_config("#define HAVE_LIBZ 1"));
+	skip "postgres was not built with ZLIB support, or Windows is involved", 5
+	  if (!check_pg_config("#define HAVE_LIBZ 1") || $windows_os);
 
 	# Generate more WAL worth one completed, compressed, segment.
 	$primary->psql('postgres', 'SELECT pg_switch_wal();');