if you want them removed,
        also add them to <literal>EXTRA_CLEAN</literal> or add your own rules to do it.
       </para>
       <para>
        It is legal to use both variables for the same module, or any
        combination, unless you have two module names in the
        <literal>MODULES</literal> list that differ only by the presence of a
        prefix <literal>built_</literal>, which would cause ambiguity. In
        that (hopefully unlikely) case, you should use only the
        <literal>HEADERS_built_$MODULE</literal> variables.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-scripts">
      <term><varname>SCRIPTS</varname></term>
      <listitem>
       <para>
        script files (not binaries) to install into
        <literal><replaceable>prefix</replaceable>/bin</literal>
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-scripts-built">
      <term><varname>SCRIPTS_built</varname></term>
      <listitem>
       <para>
        script files (not binaries) to install into
        <literal><replaceable>prefix</replaceable>/bin</literal>,
        which need to be built first
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-regress">
      <term><varname>REGRESS</varname></term>
      <listitem>
       <para>
        list of regression test cases (without suffix), see below
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-regress-opts">
      <term><varname>REGRESS_OPTS</varname></term>
      <listitem>
       <para>
        additional switches to pass to <application>pg_regress</application>
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-isolation">
      <term><varname>ISOLATION</varname></term>
      <listitem>
       <para>
        list of isolation test cases, see below for more details
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-isolation-opts">
      <term><varname>ISOLATION_OPTS</varname></term>
      <listitem>
       <para>
        additional switches to pass to
        <application>pg_isolation_regress</application>
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-tap-tests">
      <term><varname>TAP_TESTS</varname></term>
      <listitem>
       <para>
        switch defining if TAP tests need to be run, see below
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-no-install">
      <term><varname>NO_INSTALL</varname></term>
      <listitem>
       <para>
        don't define an <literal>install</literal> target, useful for test
        modules that don't need their build products to be installed
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-no-installcheck">
      <term><varname>NO_INSTALLCHECK</varname></term>
      <listitem>
       <para>
        don't define an <literal>installcheck</literal> target, useful e.g., if tests require special configuration, or don't use <application>pg_regress</application>
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-extra-clean">
      <term><varname>EXTRA_CLEAN</varname></term>
      <listitem>
       <para>
        extra files to remove in <literal>make clean</literal>
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-pg-cppflags">
      <term><varname>PG_CPPFLAGS</varname></term>
      <listitem>
       <para>
        will be prepended to <varname>CPPFLAGS</varname>
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-pg-cflags">
      <term><varname>PG_CFLAGS</varname></term>
      <listitem>
       <para>
        will be appended to <varname>CFLAGS</varname>
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="extend-pgxs-pg-cxxflags">
      <term><varname>PG_CXXFLAGS</varname></term>