Fix a chapter number

git-svn-id: http://svn.linuxfromscratch.org/LFS/branches/cross2@11903 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter08/introduction.xml

@@ -44,7 +44,8 @@
   descriptions of these) that the package installs.</para>
 
   <note><para>The SBU values and required disk space includes
-  test suite data for all applicable packages in Chapter&nbsp;6.</para></note>
+  test suite data for all applicable packages in
+  <xref linkend="chapter-building-system"/>.</para></note>
 
   <sect2>
     <title>About libraries</title>