[c++17] Suppress std::iterator deprecation warning

This change suppresses std::iterator deprecation warning in
flatbuffers.h. This new warning is enforced in latest clang.

Bug: 78646
Change-Id: Ie9b20c0c0f35e258503e55a0b2120ea23db754d9
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/flatbuffers/+/543605
Reviewed-by: Shai Barack <shayba@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index c6ccd2e..e7db5c7 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -22,7 +22,12 @@
   ]
 
   configs += [ ":flatbuffers_warnings" ]
-  public_configs = [ ":flatbuffers_config" ]
+  public_configs = [
+    ":flatbuffers_config",
+
+    # TODO(fxbug.dev/78646) Remove this config after std::iterator usages are cleaned up.
+    "//build/config:suppress_iterator_warnings",
+  ]
 
   # TODO(46773): UBSan has found an instance of undefined behavior in this target.
   # Disable UBSan for this target temporarily until it is migrated into CI/CQ.