Mark C enums as semantic2done to prevent segfaults in final switch

Author: abulgit

compiler/src/dmd/importc.d

@@ -751,6 +751,8 @@ void cEnumSemantic(Scope* sc, EnumDeclaration ed)
     }
 
     ed.memtype = commonType;
-    ed.semanticRun = PASS.semanticdone;
+    // Set semantic2done to mark C enums as fully processed
+    // Prevents issues with final switch statements that reference C enums
+    ed.semanticRun = PASS.semantic2done;
     return;
 }