WiP Fix issue allegro#21: "node-worker don't run in windows"

- in transport.send(), only call pipe.write once
- do not concat buffers when not on Windows (perf)

Payload of second call (containing `serializedMessage`) was getting lost, or at least not being received.

This appears to have _sort of_ fixed it...

I could not discern the exact root cause (something something pipes on windows).

Tests are still all passing on linux. Some failures on windows.

lib/worker/transport.js

@@ -1,3 +1,4 @@
+const os = require("os");
 const EventEmitter = require('events');
 const msgpack = require("msgpack-lite");
 
@@ -52,11 +53,24 @@ class Transport extends EventEmitter {
 
     send(message) {
         const serializedMessage = msgpack.encode(message);
-        const header = new Uint32Array([ serializedMessage.byteLength ]);
+        const payloadLength = serializedMessage.byteLength;
 
-        this.pipe.write(Buffer.from(header.buffer));
-        this.pipe.write(serializedMessage);
+        const header = new Uint32Array([payloadLength]);
+
+        if (os.platform() === "win32") {
+            const headerLength = Uint32Array.BYTES_PER_ELEMENT * header.length;
+            this.pipe.write(
+                Buffer.concat(
+                    [Buffer.from(header.buffer), serializedMessage],
+                    payloadLength + headerLength
+                )
+            );
+        }
+        else {
+            this.pipe.write(Buffer.from(header.buffer));
+            this.pipe.write(serializedMessage);
+        }
     }
 }
 
-module.exports = Transport;
+module.exports = Transport;