Look for BND annotation on classpath

The processor lives in the annotation processor path, so `Class.forName` does **not** check for the presence of the BND annotation on the classpath.

Author: ppkarwasz

log4j-plugin-processor/src/main/java/org/apache/logging/log4j/plugin/processor/PluginProcessor.java

@@ -315,13 +315,9 @@ private String commonPrefix(final String str1, final String str2) {
         return str1.substring(0, minLength);
     }
 
-    private static boolean isServiceConsumerClassPresent() {
-        try {
-            Class.forName("aQute.bnd.annotation.spi.ServiceConsumer");
-            return true;
-        } catch (ClassNotFoundException e) {
-            return false;
-        }
+    private boolean isServiceConsumerClassPresent() {
+        // Looks for the presence of the annotation on the classpath, not the annotation processor path.
+        return processingEnv.getElementUtils().getTypeElement("aQute.bnd.annotation.spi.ServiceConsumer") != null;
     }
 
     private void handleOptions(Map<String, String> options) {