Add iOS platform (refactor Mac into shared Apple platform impl)

Source/Tools/Flax.Build/Platforms/iOS/iOSPlatform.cs

@@ -0,0 +1,34 @@
+// Copyright (c) 2012-2023 Wojciech Figat. All rights reserved.
+
+namespace Flax.Build.Platforms
+{
+    /// <summary>
+    /// The build platform for all iOS systems.
+    /// </summary>
+    /// <seealso cref="UnixPlatform" />
+    public sealed class iOSPlatform : ApplePlatform
+    {
+        /// <inheritdoc />
+        public override TargetPlatform Target => TargetPlatform.iOS;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Flax.Build.Platforms.iOSPlatform"/> class.
+        /// </summary>
+        public iOSPlatform()
+        {
+            if (Platform.BuildTargetPlatform != TargetPlatform.Mac)
+                return;
+            if (!HasRequiredSDKsInstalled)
+            {
+                Log.Warning("Missing XCode. Cannot build for iOS platform.");
+                return;
+            }
+        }
+
+        /// <inheritdoc />
+        protected override Toolchain CreateToolchain(TargetArchitecture architecture)
+        {
+            return new iOSToolchain(this, architecture);
+        }
+    }
+}