fix two wrong hardcoded Chapter numbers, replacing with xrefs

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11958 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

part3intro/toolchaintechnotes.xml

@@ -309,11 +309,13 @@ checking what linker to use... /mnt/lfs/tools/i686-lfs-linux-gnu/bin/ld</compute
     and generally does not rely on toolchain defaults.</para>
 
     <para>As said above, the standard C++ library is compiled next, followed in
-    Chapter 6 by all the programs that need themselves to be built. The install
+    <xref linkend="chapter-cross-tools"/> by all the programs that need
+    themselves to be built. The install
     step of libstdc++ uses the <envar>DESTDIR</envar> variable to have the
     programs land into the LFS filesystem.</para>
 
-    <para>In Chapter 7 the native lfs compiler is built. First binutils-pass2,
+    <para>In <xref linkend="chapter-temporary-tools"/> the native lfs
+    compiler is built. First binutils-pass2,
     with the same <envar>DESTDIR</envar> install as the other programs is
     built, and then the second pass of GCC is constructed, omitting libstdc++
     and other non-important libraries.  Due to some weird logic in GCC's