Android: fix logcat not fetched when app exits/crash at start

Application output from logcat might not work if an app
crashes at the start, so with this patch we avoid that by
making logcat process fetch logs faster by not getting
the full logs but only the logs starting from the moment
we start the app (using -T arg).

This can be very annoying bug, because when starting the
app from QC it usually only prints "app_package_name died."
which forces the user to go into the logcat manually and
search for an error from thousands of lines.

Change-Id: Ic5ac0389cb28e7c80586490877a697272f3648af
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/android/androidrunnerworker.h

@@ -78,6 +78,7 @@ private:
     bool deviceFileExists(const QString &filePath);
     bool packageFileExists(const QString& filePath);
     bool uploadDebugServer(const QString &debugServerFileName);
+    void asyncStartLogcat();
 
     enum class JDBState {
         Idle,