add way to disable forge hard mixin remaps

Author: Jab125

src/main/java/dev/architectury/transformer/transformers/BuiltinProperties.java

@@ -37,5 +37,6 @@ public class BuiltinProperties {
     public static final String PLATFORM_NAME = "architectury.platform.name";
     public static final String PLATFORM_PACKAGE = "architectury.platform.package";
     public static final String FORGE_PRODUCTION_NAMESPACE = "architectury.forge.production_namespace";
+    public static final String FORGE_FIX_MIXINS = "architectury.forge.fix_mixins";
     public static final String NEOFORGE_LIKE_REMAPS = "architectury.neoforge.forgelike_remaps";
 }

src/main/java/dev/architectury/transformer/transformers/TransformForgeEnvironment.java

@@ -45,9 +45,12 @@ public class TransformForgeEnvironment implements TinyRemapperTransformer {
 
     @Override
     public List<IMappingProvider> collectMappings() throws Exception {
-        List<IMappingProvider> providers = mapMixin();
-        providers.add(remapEnvironment());
-        return providers;
+        boolean fixMixins = System.getProperty(BuiltinProperties.FORGE_FIX_MIXINS, "true").equals("true");
+        if (fixMixins) {
+            List<IMappingProvider> providers = mapMixin();
+            providers.add(remapEnvironment());
+            return providers;
+        } else return new ArrayList<>(Collections.singletonList(remapEnvironment()));
     }
 
     private IMappingProvider remapEnvironment() {