zipomatic: notify an error when /bin/zip is missing

Since zip has been outsourced, it's possible to loose it when
upgrading, in which case ZOM went busylooping without noticing the
thread actually never started.

At least now it says "failed to create the archive".

Maybe it should try to install zip?

src/add-ons/tracker/zipomatic/ZipperThread.cpp

@@ -220,6 +220,10 @@ ZipperThread::ThreadShutdown()
 void
 ZipperThread::ThreadStartupFailed(status_t status)
 {
+	fprintf(stderr, "ZipperThread::ThreadStartupFailed(): %s\n",
+		strerror(status));
+	_SendMessageToWindow(ZIPPO_THREAD_EXIT_ERROR);
+
 	Quit();
 }
 
@@ -228,9 +232,12 @@ void
 ZipperThread::ExecuteUnitFailed(status_t status)
 {
 	if (status == EOF) {
+		fprintf(stderr, "ZipperThread::ExecuteUnitFailed(): EOF\n");
 		// thread has finished, been quit or killed, we don't know
 		_SendMessageToWindow(ZIPPO_THREAD_EXIT);
 	} else {
+		fprintf(stderr, "ZipperThread::ExecuteUnitFailed(): %s\n",
+			strerror(status));
 		// explicit error - communicate error to Window
 		_SendMessageToWindow(ZIPPO_THREAD_EXIT_ERROR);
 	}