Silence GCC warning by marking an assert-only variable as unused.

llvm-svn: 96459
diff --git a/clang/lib/CodeGen/CGVtable.cpp b/clang/lib/CodeGen/CGVtable.cpp
index d2aba20..2b8b064 100644
--- a/clang/lib/CodeGen/CGVtable.cpp
+++ b/clang/lib/CodeGen/CGVtable.cpp
@@ -1168,7 +1168,7 @@
   
 void VtableBuilder::LayoutPrimaryAndAndSecondaryVtables(BaseSubobject Base,
                                                         bool BaseIsVirtual) {
-  const CXXRecordDecl *RD = Base.getBase();
+  const CXXRecordDecl *RD ATTRIBUTE_UNUSED = Base.getBase();
   assert(RD->isDynamicClass() && "class does not have a vtable!");
 
   // Add vcall and vbase offsets for this vtable.