Store a static reference to the IPC socket

This lets us use it to open files inside code-server from outside of
code-server.

To test this:
1. run code-server
2. open file outside of code-server i.e. `code-server <path-to-file`

It should open in your existing code-server instance.

Index: code-server/lib/vscode/src/vs/workbench/api/node/extHostExtensionService.ts
===================================================================
--- code-server.orig/lib/vscode/src/vs/workbench/api/node/extHostExtensionService.ts
+++ code-server/lib/vscode/src/vs/workbench/api/node/extHostExtensionService.ts
@@ -2,7 +2,9 @@
  *  Copyright (c) Microsoft Corporation. All rights reserved.
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
-
+import { promises as fs } from 'fs';
+import * as os from 'os'
+import * as path from 'vs/base/common/path';
 import * as performance from 'vs/base/common/performance';
 import { createApiFactoryAndRegisterActors } from 'vs/workbench/api/common/extHost.api.impl';
 import { RequireInterceptor } from 'vs/workbench/api/common/extHostRequireInterceptor';
@@ -72,6 +74,10 @@ export class ExtHostExtensionService ext
 		if (this._initData.remote.isRemote && this._initData.remote.authority) {
 			const cliServer = this._instaService.createInstance(CLIServer);
 			process.env['VSCODE_IPC_HOOK_CLI'] = cliServer.ipcHandlePath;
+
+			fs.writeFile(path.join(os.tmpdir(), 'vscode-ipc'), cliServer.ipcHandlePath).catch((error) => {
+				this._logService.error(error);
+			});
 		}
 
 		// Module loading tricks