Prevent child zombie process from tearing down Hyprland IPC

In rare circumstances, we may fork(), e.g., as part of a custom module,
and the child process may fail to exec() and exit. In those cases, the
IPC destructor will be called in the child process.

Prior to this commit, this call would then result in the shared socket
being closed. Prevent this by only closing the socket from the original
process.

Fixes #3975 and #4152.

Signed-off-by: Lukas Fleischer <lfleischer@lfos.de>

include/modules/hyprland/backend.hpp

@@ -42,6 +42,7 @@ class IPC {
   util::JsonParser parser_;
   std::list<std::pair<std::string, EventHandler*>> callbacks_;
   int socketfd_;  // the hyprland socket file descriptor
+  pid_t socketOwnerPid_;
   bool running_ = true;
 };