Specify a new client_plugindir path, to be used during testing

When testing installed packages, the client (mariadb or mysql) can have
plugins stored in a separate location compared to server. This change
ensures that the correct paths are used for the plugin-dir directive in
the my.cnf generated by mysql-test-run.

The directives in my.cnf will be replaced like so:

[client]
plugin-dir=$client_plugindir

[mysqld]
plugin-dir=$plugindir

where $<variable-name> corresponds to the variable name in mtr.

mysql-test/include/default_client.cnf

@@ -3,9 +3,6 @@
 # when running tests - not to depend on the current machine localization.
 #
 
-[client]
-plugin-dir=@mysqld.1.plugin-dir
-
 [mysql]
 default-character-set=latin1
 

mysql-test/lib/My/ConfigFactory.pm

@@ -216,6 +216,7 @@ my @mysqld_rules=
 my @client_rules=
 (
  { 'character-sets-dir' => \&fix_charset_dir },
+ { 'plugin-dir' => sub { $::client_plugindir } },
 );
 
 

mysql-test/mysql-test-run.pl

@@ -130,6 +130,7 @@ our $path_testlog;
 our $default_vardir;
 our $opt_vardir;                # Path to use for var/ dir
 our $plugindir;
+our $client_plugindir;
 my $path_vardir_trace;          # unix formatted opt_vardir for trace files
 my $opt_tmpdir;                 # Path to use for tmp/ dir
 my $opt_tmpdir_pid;
@@ -2784,12 +2785,15 @@ sub setup_vardir() {
   # and make them world readable
   copytree("$glob_mysql_test_dir/std_data", "$opt_vardir/std_data", "0022");
 
-  # create a plugin dir and copy or symlink plugins into it
   unless($plugindir)
   {
+    # create a plugin dir and copy or symlink plugins into it
     if ($source_dist)
     {
       $plugindir="$opt_vardir/plugins";
+      # Source builds collect both client plugins and server plugins in the
+      # same directory.
+      $client_plugindir= $plugindir;
       mkpath($plugindir);
       if (IS_WINDOWS)
       {
@@ -2845,10 +2849,18 @@ sub setup_vardir() {
            <$bindir/lib/plugin/*.so>,             # bintar
            <$bindir/lib/plugin/*.dll>)
       {
-        my $pname=basename($_);
+        my $pname= basename($_);
         set_plugin_var($pname);
-        $plugindir=dirname($_) unless $plugindir;
+        $plugindir= dirname($_) unless $plugindir;
       }
+
+      # Note: client plugins can be installed separately from server plugins,
+      #       as is the case for Debian packaging.
+      for (<$bindir/lib/*/libmariadb3/plugin>)
+      {
+        $client_plugindir= $_ if <$_/*.so>;
+      }
+      $client_plugindir= $plugindir unless $client_plugindir;
     }
   }