Avoid LDAP TAP tests when not built with LDAP

Since `run_misc_tests()` globs the test directories for test modules and
runs them directly, the `if ($ENV{with_ldap} ne 'yes')` bits of the
`Makefile` for `ldap_password_func`, at least, doesn't seem to trigger
properly. So follow the precedent of checking for SSL configuration and
skip LDAP tests when `--with-ldap` (or equivalent) hasn't been
specified.

This presumably wont't come up previously unless TAP tests were enabled
and LDAP was not configured.

While at it, fix a "Use of uninitialized value in pattern match"
warning.

Author: theory

run_build.pl

@@ -2479,6 +2479,11 @@ sub run_misc_tests
 	  ? $config_opts->{openssl}
 	  : (grep { $_ eq '--with-openssl' } @$config_opts);
 
+	my $using_ldap =
+		$using_msvc
+	  ? $config_opts->{ldap}
+	  : (grep { $_ eq '--with-ldap' } @$config_opts);
+
 	## no critic (CodeLayout::ProhibitHardTabs)
 	foreach my $testdir (
 		glob(
@@ -2490,6 +2495,7 @@ sub run_misc_tests
 	{
 		my $testname = basename($testdir);
 		next if $testname =~ /ssl/ && !$using_ssl;
+		next if $testname =~ /ldap/ && !$using_ldap;
 		next unless -d "$testdir/t";
 		next if $using_msvc && $testname eq 'pg_bsd_indent';
 		next unless step_wanted("module-$testname");
@@ -2507,7 +2513,7 @@ sub run_misc_tests
 		next unless scalar glob("$testdir/*.o $testdir/*.obj");
 
 		# skip sepgsql unless it's marked for testing
-		next if $testname eq 'sepgsql' && $ENV{PG_TEST_EXTRA} !~ /\bsepgsql\b/;
+		next if $testname eq 'sepgsql' && ($ENV{PG_TEST_EXTRA} || '') !~ /\bsepgsql\b/;
 		next unless step_wanted("contrib-$testname");
 		print time_str(), "running contrib test $testname ...\n" if $verbose;
 		run_tap_test("$testdir", "contrib-$testname", undef);