Fix iterator invalidation. PR16935.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188835 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/driver/driver.cpp b/tools/driver/driver.cpp
index 11fa4d2..88863ab 100644
--- a/tools/driver/driver.cpp
+++ b/tools/driver/driver.cpp
@@ -269,9 +269,10 @@
     SmallVectorImpl<const char *>::iterator it = ArgVector.begin();
     if (it != ArgVector.end())
       ++it;
-    ArgVector.insert(it, SaveStringInSet(SavedStrings, Prefix));
-    ArgVector.insert(it,
-      SaveStringInSet(SavedStrings, std::string("-target")));
+    const char* Strings[] =
+      { SaveStringInSet(SavedStrings, std::string("-target")),
+        SaveStringInSet(SavedStrings, Prefix) };
+    ArgVector.insert(it, Strings, Strings + llvm::array_lengthof(Strings));
   }
 }