Fixed the daemon process termination.

From now on, we spawn a detached process that
will periodically check whether the parent Theia
the process is alive, if no, terminates the daemon.

Signed-off-by: Akos Kitta <kittaakos@typefox.io>

arduino-ide-extension/src/node/daemon-watcher.ts

@@ -0,0 +1,17 @@
+import * as psTree from 'ps-tree';
+const kill = require('tree-kill');
+const [theiaPid, daemonPid] = process.argv.slice(2).map(id => Number.parseInt(id, 10));
+
+setInterval(() => {
+    try {
+        // Throws an exception if the Theia process doesn't exist anymore.
+        process.kill(theiaPid, 0);
+    } catch {
+        psTree(daemonPid, function (_, children) {
+            for (const { PID } of children) {
+                kill(PID);
+            }
+            kill(daemonPid, () => process.exit());
+        });
+    }
+}, 1000);