Utils/File: Fix handle releasing

ShouldClose was never being set in the event we opened a regular file.
The only time it was set (to false) is when it's used to encapsulate
stderr and stdout.

So anything opened by a File instance was essentially held open.

FEXCore/include/FEXCore/Utils/File.h

@@ -58,6 +58,8 @@ public:
     }
     IsValidHandle = Handle != INVALID_HANDLE_VALUE;
 #endif
+
+    ShouldClose = IsValidHandle;
   }
 
   /**