mention rdynamic, PR3431, patch by Stein Roger Skafløtten!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64106 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/tutorial/LangImpl4.html b/docs/tutorial/LangImpl4.html
index 8f5e054..95a8b6d 100644
--- a/docs/tutorial/LangImpl4.html
+++ b/docs/tutorial/LangImpl4.html
@@ -501,6 +501,11 @@
 </pre>
 </div>
 
+<p>
+If you are compiling this on Linux, make sure to add the "-rdynamic" option 
+as well.  This makes sure that the external functions are resolved properly 
+at runtime.</p>
+
 <p>Here is the code:</p>
 
 <div class="doc_code">