Fix build for LLVM's remove transitive includes (#6802) In the latest LLVM roll this file requires the iterator header for std::back_inserter I believe LLVM has recently removed transitive includes by default, see: https://github.com/llvm/llvm-project/commit/ce5b2e876494cb95f02d9f915081e2b8781e74d1

diff --git a/source/val/validate_cfg.cpp b/source/val/validate_cfg.cpp
index a4d2a66..cdded6a 100644
--- a/source/val/validate_cfg.cpp
+++ b/source/val/validate_cfg.cpp

@@ -15,6 +15,7 @@
 #include <cassert>
 #include <functional>
 #include <iostream>
+#include <iterator>
 #include <map>
 #include <string>
 #include <tuple>