Add vendor to improve building speed.

This also adds ability to be built in network-constrained environment.

vendor/golang.org/x/crypto/sha3/hashes_generic.go

@@ -0,0 +1,27 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !gc || purego || !s390x
+
+package sha3
+
+import (
+	"hash"
+)
+
+// new224Asm returns an assembly implementation of SHA3-224 if available,
+// otherwise it returns nil.
+func new224Asm() hash.Hash { return nil }
+
+// new256Asm returns an assembly implementation of SHA3-256 if available,
+// otherwise it returns nil.
+func new256Asm() hash.Hash { return nil }
+
+// new384Asm returns an assembly implementation of SHA3-384 if available,
+// otherwise it returns nil.
+func new384Asm() hash.Hash { return nil }
+
+// new512Asm returns an assembly implementation of SHA3-512 if available,
+// otherwise it returns nil.
+func new512Asm() hash.Hash { return nil }