I just ran into the following issue when building a project with ring = "0.17.1" as dependency:

crypto/curve25519/curve25519_64_adx.c:23:10: fatal error: ../../third_party/fiat/curve25519_64_adx.h: No such file or directory
     23 | #include "../../third_party/fiat/curve25519_64_adx.h"

The file curve25519_64_adx.h is not present in the fiat directory.
I guess it is missing in the list here: https://github.com/briansmith/ring/blob/main/Cargo.toml#L144

Building with dependency ring = { git = "https://github.com/briansmith/ring", rev = "2afc921" } works fine.

I am just wondering why I am the only one having this problem....