Fix LDAP schema path for Debian. This permits to enable LDAP tests during build

lemonldap-ng-portal/t/test-ldap.pm

@@ -3,7 +3,11 @@
 if ( $ENV{LLNGTESTLDAP} ) {
     my $slapd_bin   = $ENV{LLNGTESTLDAP_SLAPD_BIN}   || '/usr/sbin/slapd';
     my $slapadd_bin = $ENV{LLNGTESTLDAP_SLAPADD_BIN} || '/usr/sbin/slapadd';
-    my $slapd_schema_dir = $ENV{LLNGTESTLDAP_SCHEMA_DIR} || '/etc/slapd/schema';
+    my $slapd_schema_dir =
+      ( $ENV{LLNGTESTLDAP_SCHEMA_DIR}
+          and -d $ENV{LLNGTESTLDAP_SCHEMA_DIR} ? $ENV{LLNGTESTLDAP_SCHEMA_DIR}
+        : -d '/etc/slapd/schema' ? '/etc/slapd/schema'
+        :                          '/etc/ldap/schema' );
     eval { mkdir 't/testslapd/slapd.d' };
     eval { mkdir 't/testslapd/data' };
     system('cp t/testslapd/slapd.ldif t/testslapd/slapd-test.ldif');