Add a warning before installation of glibc-chapter5

git-svn-id: http://svn.linuxfromscratch.org/LFS/branches/cross2@11907 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter05/glibc.xml

@@ -157,6 +157,12 @@ cd       build</userinput></screen>
 
     <para>Install the package:</para>
 
+    <warning><para>If <envar>LFS</envar> is not proprly set, and despite the
+    recommendations, you are building as root, the next command will install
+    the newly built glibc to your host system, which most likely will render it
+    unusable. So double check that the environment is correctly set for user
+    <systemitem class="username">lfs</systemitem>.</para></warning>
+
 <screen><userinput remap="install">make DESTDIR=$LFS install</userinput></screen>
 
     <variablelist>