Implement SDL platform, windowing and input handling

Source/Tools/Flax.Build/Configuration.cs

@@ -276,6 +276,12 @@ namespace Flax.Build
         [CommandLine("useDotNet", "1 to enable .NET support in build, 0 to enable Mono support in build")]
         public static bool UseDotNet = true;
 
+        /// <summary>
+        /// True if SDL support should be enabled.
+        /// </summary>
+        [CommandLine("useSdl", "1 to enable SDL support in build")]
+        public static bool UseSDL = true;
+
         public static bool WithCSharp(NativeCpp.BuildOptions options)
         {
             return UseCSharp || options.Target.IsEditor;
@@ -291,5 +297,10 @@ namespace Flax.Build
         {
             return UseDotNet;
         }
+
+        public static bool WithSDL(NativeCpp.BuildOptions options)
+        {
+            return UseSDL;
+        }
     }
 }