Make sure that our system folder is 755

See #364

F-Droid/src/org/fdroid/fdroid/installer/InstallIntoSystem.java

@@ -177,6 +177,7 @@ abstract class InstallIntoSystem {
         protected List<String> getCopyToSystemCommands() {
             List<String> commands = new ArrayList<>(3);
             commands.add("mkdir " + getSystemFolder()); // create app directory if not existing
+            commands.add("chmod 755 " + getSystemFolder());
             commands.add("cat " + context.getPackageCodePath() + " > " + getInstallPath() + ".tmp");
             commands.add("chmod 644 " + getInstallPath() + ".tmp");
             return commands;