Fix some issues with TAP tests for postgres -C

This addresses two issues with the tests added in 0c39c292 for runtime
GUCs:
- Re-enable the test on Msys.  The test could fail because of \r\n
generated by Msys perl.  0d91c52a has taken care of this issue.
- Allow the test to run in the context of a privileged account.  CIs
running under privileged accounts would fail on permission failures, as
reported by Andres Freund.  This issue is fixed by wrapping the postgres
command within pg_ctl as the latter will take care of any permissions
needed.  The test checking a failure of postgres -C for a runtime
parameter with an instance running is removed, as pg_ctl produces an
unstable error code (no need for a CI to reproduce that).

Discussion: https://postgr.es/m/20210921032040.lyl4lcax37aedx2x@alap3.anarazel.de

src/bin/pg_checksums/t/002_actions.pl

@@ -11,7 +11,7 @@ use PostgresNode;
 use TestLib;
 
 use Fcntl qw(:seek);
-use Test::More tests => 69;
+use Test::More tests => 66;
 
 
 # Utility routine to create and check a table with corrupted checksums
@@ -181,34 +181,25 @@ command_fails(
 
 # Test postgres -C for an offline cluster.
 # Run-time GUCs are safe to query here.  Note that a lock file is created,
-# then unlinked, leading to an extra LOG entry showing in stderr.
-SKIP:
-{
-	skip "unstable output generated with Msys", 3
-	  if ($Config{osname} eq 'msys');
-	command_checks_all(
-		[ 'postgres', '-D', $pgdata, '-C', 'data_checksums' ],
-		0,
-		[qr/^on$/],
-		# LOG entry when unlinking lock file.
-		[qr/database system is shut down/],
-		'data_checksums=on is reported on an offline cluster');
-}
+# then removed, leading to an extra LOG entry showing in stderr.  This uses
+# log_min_messages=fatal to remove any noise.  This test uses a startup
+# wrapped with pg_ctl to allow the case where this runs under a privileged
+# account on Windows.
+command_checks_all(
+	[
+		'pg_ctl', 'start', '-D', $pgdata, '-s', '-o',
+		'-C data_checksums -c log_min_messages=fatal'
+	],
+	1,
+	[qr/^on$/],
+	[qr/could not start server/],
+	'data_checksums=on is reported on an offline cluster');
 
 # Checks cannot happen with an online cluster
 $node->start;
 command_fails([ 'pg_checksums', '--check', '-D', $pgdata ],
 	"fails with online cluster");
 
-# Test postgres -C on an online cluster.
-command_fails_like(
-	[ 'postgres', '-D', $pgdata, '-C', 'data_checksums' ],
-	qr/lock file .* already exists/,
-	'data_checksums is not reported on an online cluster');
-command_ok(
-	[ 'postgres', '-D', $pgdata, '-C', 'work_mem' ],
-	'non-runtime parameter is reported on an online cluster');
-
 # Check corruption of table on default tablespace.
 check_relation_corruption($node, 'corrupt1', 'pg_default');