Fix iterator invalidation bug, identified by Coverity.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28257 91177308-0d34-0410-b5e6-96231b3b80d8

lib/System/DynamicLibrary.cpp

@@ -93,6 +93,7 @@ DynamicLibrary::~DynamicLibrary() {
       if (*I == a_handle) {
         // Note: don't use the swap/pop_back trick here. Order is important.
         OpenedHandles.erase(I);
+        return;
       }
     }
   }