Add note about symlink reqt in Host Requirements

Add simple compilation check in Host Requirements

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@8583 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

prologue/hostreqs.xml

@@ -22,7 +22,7 @@
 
     <listitem>
       <para><emphasis role="strong">Bash-2.05a</emphasis> (/bin/sh
-      must be a symbolic or hard link to bash)</para>
+      should be a symbolic or hard link to bash)</para>
     </listitem>
 
     <listitem>
@@ -33,7 +33,7 @@
 
     <listitem>
       <para><emphasis role="strong">Bison-1.875</emphasis> (/usr/bin/yacc
-      must be a link to bison or small script that executes bison)</para>
+      should be a link to bison or small script that executes bison)</para>
     </listitem>
 
     <listitem>
@@ -55,7 +55,7 @@
 
     <listitem>
       <para><emphasis role="strong">Gawk-3.0</emphasis> (/usr/bin/awk
-      must be a link to gawk)</para>
+      should be a link to gawk)</para>
     </listitem>
 
     <listitem>
@@ -128,7 +128,16 @@
 
   </itemizedlist>
 
-  <para>To see whether your host system has all the appropriate versions, run the following:</para>
+  <para>Note that the symlinks mentioned above are required to build an LFS
+  system using the instructions contained within this book. Symlinks that
+  point to other software (such as dash, mawk, etc.) may work, but are not
+  tested or supported by the LFS development team, and may require either
+  deviation from the instructions or additional patches to some
+  packages.</para>
+
+  <para>To see whether your host system has all the appropriate versions, and
+  ability to compile programs, run
+  the following:</para>
 
 <screen role="nodump"><userinput>cat &gt; version-check.sh &lt;&lt; "EOF"
 <literal>#!/bin/bash
@@ -160,6 +169,9 @@ echo Perl `perl -V:version`
 sed --version | head -n1
 tar --version | head -n1
 makeinfo --version | head -n1
+echo 'main(){}' > dummy.c &amp;&amp; gcc -o dummy dummy.c
+if [ -x dummy ]; then echo "Compilation OK"; else echo "Compilation failed"; fi
+rm -f dummy.c dummy
 </literal>
 EOF