BootManager: Avoid Global System Accessor

Source/Core/Core/BootManager.h

@@ -5,12 +5,17 @@
 
 #include <memory>
 
+namespace Core
+{
+class System;
+}
 struct BootParameters;
 struct WindowSystemInfo;
 
 namespace BootManager
 {
-bool BootCore(std::unique_ptr<BootParameters> parameters, const WindowSystemInfo& wsi);
+bool BootCore(Core::System& system, std::unique_ptr<BootParameters> parameters,
+              const WindowSystemInfo& wsi);
 
 // Synchronise Dolphin's configuration with the SYSCONF (which may have changed during emulation),
 // and restore settings that were overriden by per-game INIs or for some other reason.