Fix pgbench TAP test to work in VPATH builds.

Previously, it'd try to create log files under the source directory
not the build directory.  This fell over if the source isn't writable
by the building user.

Fabien Coelho

Discussion: https://postgr.es/m/alpine.DEB.2.20.1801101038340.2283@lancre

src/bin/pgbench/t/001_pgbench_with_server.pl

@@ -605,24 +605,26 @@ sub check_pgbench_logs
 	ok(unlink(@logs), "remove log files");
 }
 
+my $bdir = $node->basedir;
+
 # with sampling rate
 pgbench(
-'-n -S -t 50 -c 2 --log --log-prefix=001_pgbench_log_2 --sampling-rate=0.5',
+"-n -S -t 50 -c 2 --log --log-prefix=$bdir/001_pgbench_log_2 --sampling-rate=0.5",
 	0,
 	[ qr{select only}, qr{processed: 100/100} ],
 	[qr{^$}],
 	'pgbench logs');
 
-check_pgbench_logs('001_pgbench_log_2', 1, 8, 92,
+check_pgbench_logs("$bdir/001_pgbench_log_2", 1, 8, 92,
 	qr{^0 \d{1,2} \d+ \d \d+ \d+$});
 
 # check log file in some detail
 pgbench(
-	'-n -b se -t 10 -l --log-prefix=001_pgbench_log_3',
+	"-n -b se -t 10 -l --log-prefix=$bdir/001_pgbench_log_3",
 	0, [ qr{select only}, qr{processed: 10/10} ],
 	[qr{^$}], 'pgbench logs contents');
 
-check_pgbench_logs('001_pgbench_log_3', 1, 10, 10,
+check_pgbench_logs("$bdir/001_pgbench_log_3", 1, 10, 10,
 	qr{^\d \d{1,2} \d+ \d \d+ \d+$});
 
 # done