Set CHECKED when there are no modules to avoid repeating the work (#1184)

Author: sugmanue

core/src/main/java/software/amazon/smithy/java/core/VersionCheck.java

@@ -62,6 +62,7 @@ public static void check(ModuleVersion codegenVersion) {
         }
 
         if (modules.isEmpty()) {
+            CHECKED.set(true);
             return;
         }