Add an example for the correct invocation of the pkg-install script from the

port's Makefile, specifying PKG_PREFIX and using the ${PKGINSTALL} variable.

PR:		74328
Submitted by:	"freebsd@simplerezo.com" <freebsd@simplerezo.com>

en_US.ISO8859-1/books/porters-handbook/book.sgml

@@ -5014,7 +5014,9 @@ ${PREFIX}/man/ja/man4/baz.4.gz</programlisting>
 	  <para>This script is not run automatically if you install the port
 	    with <command>make install</command>.  If you are depending on it
 	    being run, you will have to explicitly call it from your port's
-	    <filename>Makefile</filename>.</para>
+	    <filename>Makefile</filename>, with a line like
+	    <literal>PKG_PREFIX=&dollar;{PREFIX} &dollar;{SH} &dollar;{PKGINSTALL}
+	    &dollar;{PKGNAME} PRE-INSTALL</literal>.</para>
 	</note>
       </sect1>