Make C++ flags available in Rust.

In order to do this, we automagically grab all of C++ gflags and
add them into the Rust Clap command. We then pass through the flags
back to C++ to set them.

This requires different versions of clap to make both our implementation
and autocxx happy.

Change-Id: I36a9584de2ade55390f7109889996bad6e2cd071
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/third_party/autocxx/gen/cmd/BUILD b/third_party/autocxx/gen/cmd/BUILD
index 60d011c..c05e24d 100644
--- a/third_party/autocxx/gen/cmd/BUILD
+++ b/third_party/autocxx/gen/cmd/BUILD
@@ -22,7 +22,7 @@
     version = "0.16.0",
     deps = [
         "//third_party/autocxx/engine:autocxx_engine",
-        "@crate_index//:clap",
+        "@crate_index//:clap3",
         "@crate_index//:env_logger",
         "@crate_index//:indexmap",
         "@crate_index//:miette",