Avoid having /bin in lfs' PATH if the build distro has merged

/bin and /usr/bin

git-svn-id: http://svn.linuxfromscratch.org/LFS/branches/cross-chap5@11837 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter04/settingenviron.xml

@@ -43,7 +43,9 @@ umask 022
 LFS=/mnt/lfs
 LC_ALL=POSIX
 LFS_TGT=$(uname -m)-lfs-linux-gnu
-PATH=$LFS/tools/bin:/bin:/usr/bin
+PATH=/usr/bin
+if [ ! -l /bin ]; then PATH=/bin:$PATH; fi
+PATH=$LFS/tools/bin:$PATH
 export LFS LC_ALL LFS_TGT PATH</literal>
 EOF</userinput></screen>
 
@@ -108,14 +110,36 @@ EOF</userinput></screen>
     </varlistentry>
 
     <varlistentry>
-      <term><parameter>PATH=$LFS/tools/bin:/bin:/usr/bin</parameter></term>
+      <term><parameter>PATH=/usr/bin</parameter></term>
+      <listitem>
+  <para>Many modern linux distributions have merged <filename
+  class="directory">/bin</filename> and <filename
+  class="directory">/usr/bin</filename>. When this is the case, the standard
+  <envar>PATH</envar> variable needs just to be set to <filename
+  class="directory">/usr/bin/</filename> for the <xref
+  linkend="chapter-temporary-tools"/> environment. When this is not the
+  case, the following line adds <filename class="directory">/bin</filename>
+  to the path.</para>
+      </listitem>
+    </varlistentry>
+
+    <varlistentry>
+	    <term><parameter>if [ ! -l /bin ]; then PATH=/bin:$PATH; fi</parameter></term>
+      <listitem>
+  <para>If <filename class="directory">/bin</filename> is not a symbolic
+  link, then it has to be added to the <envar>PATH</envar> variable.</para>
+      </listitem>
+    </varlistentry>
+
+    <varlistentry>
+      <term><parameter>PATH=$LFS/tools/bin:$PATH</parameter></term>
       <listitem>
   <para>By putting <filename class="directory">$LFS/tools/bin</filename> ahead of the
-  standard <envar>PATH</envar>, all the programs installed in <xref
+  standard <envar>PATH</envar>, the cross-compiler installed at the beginning
-  linkend="chapter-temporary-tools"/> are picked up by the shell immediately after
+  of <xref linkend="chapter-temporary-tools"/> is picked up by the shell
-  their installation. This, combined with turning off hashing, limits the risk
+  immediately after its installation. This, combined with turning off hashing,
-  that old programs are used from the host when the same programs are available in
+  limits the risk that the compiler from the host be used instead of the
-  the Chapter 5 environment.</para>
+  cross-compiler.</para>
       </listitem>
     </varlistentry>