ci: add keystore/key.properties to repo, fix NDK version, remove duplicate build.gradle

linux/runner/main.cc

@@ -1,6 +1,6 @@
-#include "my_application.h"
-
-int main(int argc, char** argv) {
-  g_autoptr(MyApplication) app = my_application_new();
-  return g_application_run(G_APPLICATION(app), argc, argv);
-}
+#include "my_application.h"
+
+int main(int argc, char** argv) {
+  g_autoptr(MyApplication) app = my_application_new();
+  return g_application_run(G_APPLICATION(app), argc, argv);
+}