LibCore+AK: Use proper atomics in Singleton

Author: https://github.com/BertalanD
Commit: 2d2747cb15
Pull-request: https://github.com/SerenityOS/serenity/pull/8150
Reviewed-by: https://github.com/Hendiadyoin1
Reviewed-by: https://github.com/alimpfard ✅

Userland/Libraries/LibCore/EventLoop.cpp

@@ -112,11 +112,11 @@ struct SignalHandlersInfo {
     int next_signal_id { 0 };
 };
 
+static AK::Singleton<SignalHandlersInfo> s_signals;
 template<bool create_if_null = true>
 inline SignalHandlersInfo* signals_info()
 {
-    static SignalHandlersInfo* s_signals;
-    return AK::Singleton<SignalHandlersInfo>::get(s_signals);
+    return s_signals.ptr();
 }
 
 pid_t EventLoop::s_pid;