fix: Isolate mixins in alternative source sets

src/texturePacks/java/moe/nea/firmament/features/texturepack/Compat.kt

@@ -0,0 +1,11 @@
+package moe.nea.firmament.features.texturepack
+
+import moe.nea.firmament.util.compatloader.CompatMeta
+import moe.nea.firmament.util.compatloader.ICompatMeta
+
+@CompatMeta
+object Compat : ICompatMeta {
+	override fun shouldLoad(): Boolean {
+		return true
+	}
+}