chunks: fix DiscoverVersionIterative build error

refs #3681

Change-Id: I00109197d05bc480a249f74b123e9a553acb25a3
diff --git a/tools/chunks/catchunks/discover-version-iterative.cpp b/tools/chunks/catchunks/discover-version-iterative.cpp
index 4f2f543..98ca5dd 100644
--- a/tools/chunks/catchunks/discover-version-iterative.cpp
+++ b/tools/chunks/catchunks/discover-version-iterative.cpp
@@ -84,8 +84,9 @@
     m_strayExcludes.excludeOne(name[versionindex]);
   }
 
-  for (const auto& i : m_strayExcludes) {
-    exclude.excludeOne(i.first);
+  for (const Exclude::Range& range : m_strayExcludes) {
+    BOOST_ASSERT(range.isSingular());
+    exclude.excludeOne(range.from);
   }
 
   Interest newInterest(interest);