For some (unknown) reason, GNUNET uses Ed25519 curve with no flags, while it is intended to be used with `(flags eddsa)` in libgcrypt.
GNUNET's two tests (in src/util) fail with libgcrypt master (to be 1.9.0), while it goes well with 1.8.x.
```
FAIL: test_crypto_ecdh_ecdsa
FAIL: test_crypto_ecc_dlog
```