add a con of clang vs gcc

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@44882 91177308-0d34-0410-b5e6-96231b3b80d8

www/comparison.html

@@ -53,6 +53,9 @@
     <li>GCC front-ends are very mature and already support C/C++/ObjC and all
         the variants we are interested in.  clang's support for C++ in
         particular is nowhere near what GCC supports.</li>
+    <li>GCC's codegen is much more mature than clang's right now.  clang is
+        only capable of codegen for small and simple projects and does not yet
+        support debug info.</li>
     <li>GCC is popular and widely adopted.</li>
     <li>GCC does not require a C++ compiler to build it.</li>
     </ul>