Add build tags for disabling crypto independently of cgo

no-crypto.go

@@ -0,0 +1,11 @@
+// +build !cgo nocrypto
+
+package main
+
+func NewCryptoHelper(bridge *Bridge) Crypto {
+	if !bridge.Config.Bridge.Encryption.Allow {
+		bridge.Log.Warnln("Bridge built without end-to-bridge encryption, but encryption is enabled in config")
+	}
+	bridge.Log.Debugln("Bridge built without end-to-bridge encryption")
+	return nil
+}