Modify gcc test note for Intel chips with MPX support that do NOT have it enabled in the kernel (most host systems)

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11438 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter06/gcc.xml

@@ -136,7 +136,8 @@ cd       build</userinput></screen>
       there may be more than 1100 failures in the gcc.target/i386/mpx
       tests (which are designed to test the MPX option on recent
       Intel processors). These can safely be ignored on AMD
-      processors.
+      processors. These tests will also fail on Intel processors if MPX support
+      is not enabled in the kernel even though it is present on the CPU.
     </para></note>
 
     <para>Install the package:</para>