Add role="nodump" to examples in "About SBUs"

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11468 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter04/aboutsbus.xml

@@ -68,12 +68,12 @@
 		在一个 Core2Duo 系统中，可以设置下列环境变量，
 		以支持用两个并行的进程进行编译：</para>
 
-    <screen><userinput>export MAKEFLAGS='-j 2'</userinput></screen>
+    <screen role="nodump"><userinput>export MAKEFLAGS='-j 2'</userinput></screen>
 
     <!--para>or just building with:</para-->
 	<para>或者直接用以下命令构建：</para>
 
-    <screen><userinput>make -j2</userinput></screen>
+    <screen role="nodump"><userinput>make -j2</userinput></screen>
 
     <!--para>When multiple processors are used in this way, the SBU units in the
     book will vary even more than they normally would.  In some cases, the make