env: set CONFIG_SITE to prevent potential contamination from host distro

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@12045 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter04/settingenviron.xml

@@ -46,7 +46,8 @@ LFS_TGT=$(uname -m)-lfs-linux-gnu
 PATH=/usr/bin
 if [ ! -L /bin ]; then PATH=/bin:$PATH; fi
 PATH=$LFS/tools/bin:$PATH
-export LFS LC_ALL LFS_TGT PATH</literal>
+CONFIG_SITE=$LFS/usr/share/config.site
+export LFS LC_ALL LFS_TGT PATH CONFIG_SITE</literal>
 EOF</userinput></screen>
 
   <variablelist>
@@ -144,7 +145,19 @@ EOF</userinput></screen>
     </varlistentry>
 
     <varlistentry>
-      <term><parameter>export LFS LC_ALL LFS_TGT PATH</parameter></term>
+      <term><parameter>CONFIG_SITE=$LFS/usr/share/config.site</parameter></term>
+      <listitem>
+  <para>In <xref linkend="chapter-cross-tools"/> and
+  <xref linkend="chapter-temporary-tools"/>, if this variable is not set,
+  <command>configure</command> scripts
+  will attempt to load configuration from
+  <filename>/usr/share/config.site</filename> of the host system. Override
+  it to prevent potential contamination from host.</para>
+      </listitem>
+    </varlistentry>
+
+    <varlistentry>
+      <term><parameter>export ...</parameter></term>
       <listitem>
         <para>While the above commands have set some variables, in order
         to make them visible within any sub-shells, we export them.</para>