prf redirection build fixes

Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NViktor Dukhovni <viktor@openssl.org>

crypto/kdf/tls1_prf.c

@@ -142,7 +142,7 @@ static int pkey_tls1_prf_derive(EVP_PKEY_CTX *ctx, unsigned char *key,
                                 size_t *keylen)
 {
     TLS1_PRF_PKEY_CTX *kctx = ctx->data;
-    if (kctx->md == NULL || kctx->sec == NULL || kctx->seed == NULL)
+    if (kctx->md == NULL || kctx->sec == NULL || kctx->seedlen == 0)
         return 0;
     return tls1_prf_alg(kctx->md, kctx->sec, kctx->seclen,
                         kctx->seed, kctx->seedlen,

util/mkfiles.pl

@@ -65,6 +65,7 @@ my @dirs = (
 "crypto/async",
 "crypto/chacha",
 "crypto/poly1305",
+"crypto/kdf",
 "ssl",
 "apps",
 "engines",