infra: Warn about support drop of old Windows versions (#3299)

* infra: Warn about support drop of old Windows versions

See #3298.

* Address comment

Ryujinx.Memory/WindowsShared/PlaceholderManager.cs

@@ -469,14 +469,12 @@ namespace Ryujinx.Memory.WindowsShared
         {
             ulong endAddress = address + size;
             var overlaps = Array.Empty<IntervalTreeNode<ulong, MemoryPermission>>();
-            int count = 0;
+            int count;
 
             lock (_protections)
             {
                 count = _protections.Get(address, endAddress, ref overlaps);
 
-                Debug.Assert(count > 0);
-
                 if (count == 1 &&
                     overlaps[0].Start <= address &&
                     overlaps[0].End >= endAddress &&
@@ -574,7 +572,7 @@ namespace Ryujinx.Memory.WindowsShared
         {
             ulong endAddress = address + size;
             var overlaps = Array.Empty<IntervalTreeNode<ulong, MemoryPermission>>();
-            int count = 0;
+            int count;
 
             lock (_protections)
             {

Ryujinx/Program.cs

@@ -32,8 +32,20 @@ namespace Ryujinx
         [DllImport("libX11")]
         private extern static int XInitThreads();
 
+        [DllImport("user32.dll", SetLastError = true)]
+        public static extern int MessageBoxA(IntPtr hWnd, string text, string caption, uint type);
+
+        private const uint MB_ICONWARNING = 0x30;
+
         static void Main(string[] args)
-        { 
+        {
+            Version = ReleaseInformations.GetVersion();
+
+            if (OperatingSystem.IsWindows() && !OperatingSystem.IsWindowsVersionAtLeast(10, 0, 17134))
+            {
+                MessageBoxA(IntPtr.Zero, "You are running an outdated version of Windows.\n\nStarting on June 1st 2022, Ryujinx will only support Windows 10 1803 and newer.\n", $"Ryujinx {Version}", MB_ICONWARNING);
+            }
+
             // Parse Arguments.
             string launchPathArg      = null;
             string baseDirPathArg     = null;
@@ -82,8 +94,6 @@ namespace Ryujinx
             // Delete backup files after updating.
             Task.Run(Updater.CleanupUpdate);
 
-            Version = ReleaseInformations.GetVersion();
-
             Console.Title = $"Ryujinx Console {Version}";
 
             // NOTE: GTK3 doesn't init X11 in a multi threaded way.