Disable LogbackLoggingSystem's XML support when spring.xml.ignore=true

Closes gh-22106

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/logback/LogbackLoggingSystem.java

@@ -49,6 +49,7 @@ import org.springframework.boot.logging.LoggingInitializationContext;
 import org.springframework.boot.logging.LoggingSystem;
 import org.springframework.boot.logging.LoggingSystemProperties;
 import org.springframework.boot.logging.Slf4JLoggingSystem;
+import org.springframework.core.SpringProperties;
 import org.springframework.core.env.Environment;
 import org.springframework.util.Assert;
 import org.springframework.util.ResourceUtils;
@@ -65,6 +66,9 @@ import org.springframework.util.StringUtils;
  */
 public class LogbackLoggingSystem extends Slf4JLoggingSystem {
 
+	// Static final field to facilitate code removal by Graal
+	private static final boolean XML_ENABLED = !SpringProperties.getFlag("spring.xml.ignore");
+
 	private static final String CONFIGURATION_FILE_PROPERTY = "logback.configurationFile";
 
 	private static final LogLevels<Level> LEVELS = new LogLevels<>();
@@ -172,7 +176,7 @@ public class LogbackLoggingSystem extends Slf4JLoggingSystem {
 
 	private void configureByResourceUrl(LoggingInitializationContext initializationContext, LoggerContext loggerContext,
 			URL url) throws JoranException {
-		if (url.toString().endsWith("xml")) {
+		if (XML_ENABLED && url.toString().endsWith("xml")) {
 			JoranConfigurator configurator = new SpringBootJoranConfigurator(initializationContext);
 			configurator.setContext(loggerContext);
 			configurator.doConfigure(url);