use platform-specific line separator for hint messages

The synthetic class hint message was using hardcoded \n line separators,
which caused test failures on Windows CI. Windows uses \r\n as line separator,
but the test framework splits violation messages using System.lineSeparator().
This mismatch prevented proper message parsing and matching in integration tests.

Changed SYNTHETIC_CLASS_HINT_MESSAGE from a static constant with hardcoded \n
to a dynamic method getSyntheticClassHintMessage() that uses System.lineSeparator().
This ensures the hint message uses the correct platform-specific line separator,
allowing tests to pass on all platforms (macOS, Linux, and Windows).

Signed-off-by: chadongmin <cdm2883@naver.com>

Author: chadongmin

archunit/src/main/java/com/tngtech/archunit/lang/conditions/ArchConditions.java

@@ -1308,13 +1308,15 @@ public static <T extends HasDescription & HasSourceCodeLocation> ConditionByPred
                 .describeEventsBy((predicateDescription, satisfied) -> (satisfied ? "has " : "does not have ") + predicateDescription);
     }
 
-    private static final String SYNTHETIC_CLASS_HINT_MESSAGE =
-            "\n\nHint: The failing class appears to be a synthetic or anonymous class " +
-            "generated by the compiler (e.g., from lambdas, switch expressions, or inner classes). " +
-            "To exclude these from your rule, consider adding:\n" +
-            "  .that().doNotHaveModifier(JavaModifier.SYNTHETIC)\n" +
-            "or:\n" +
-            "  .that().areNotAnonymousClasses()";
+    private static String getSyntheticClassHintMessage() {
+        String lineSeparator = System.lineSeparator();
+        return lineSeparator + lineSeparator + "Hint: The failing class appears to be a synthetic or anonymous class " +
+                "generated by the compiler (e.g., from lambdas, switch expressions, or inner classes). " +
+                "To exclude these from your rule, consider adding:" + lineSeparator +
+                "  .that().doNotHaveModifier(JavaModifier.SYNTHETIC)" + lineSeparator +
+                "or:" + lineSeparator +
+                "  .that().areNotAnonymousClasses()";
+    }
 
     /**
      * Like {@link #have(DescribedPredicate)}, but adds a helpful hint when the condition fails on synthetic or anonymous classes.
@@ -1332,7 +1334,7 @@ public void check(JavaClass javaClass, ConditionEvents events) {
                 String message;
                 if (!satisfied && isSyntheticOrAnonymous(javaClass)) {
                     message = javaClass.getDescription() + " " + baseMessage +
-                             " in " + javaClass.getSourceCodeLocation() + SYNTHETIC_CLASS_HINT_MESSAGE;
+                             " in " + javaClass.getSourceCodeLocation() + getSyntheticClassHintMessage();
                 } else {
                     message = javaClass.getDescription() + " " + baseMessage +
                              " in " + javaClass.getSourceCodeLocation();