Fix a bunch of ifdirective related issues in Ink. Load the UI rect shader in ensom.

test/hint_in_struct.ink

@@ -0,0 +1,10 @@
+#add_define UV
+
+VSInput :: struct {
+	position : float2 @position;
+	color    : float4 @color;
+
+	#if Env.UV {
+		uv : float2 @UV;
+	}
+}