Desktop: Add support for multiple instances (#11963)

packages/lib/utils/processStartFlags.ts

@@ -13,6 +13,7 @@ export interface MatchedStartFlags {
 	logLevel?: LogLevel;
 	allowOverridingDnsResultOrder?: boolean;
 	devPlugins?: string[];
+	altInstanceId?: string;
 }
 
 // Handles the initial flags passed to main script and
@@ -118,6 +119,12 @@ const processStartFlags = async (argv: string[], setDefaults = true) => {
 			continue;
 		}
 
+		if (arg === '--alt-instance-id') {
+			matched.altInstanceId = nextArg;
+			argv.splice(0, 2);
+			continue;
+		}
+
 		if (arg.indexOf('--remote-debugging-port=') === 0) {
 			// Electron-specific flag used for debugging - ignore it. Electron expects this flag in '--x=y' form, a single string.
 			argv.splice(0, 1);