Change additional metadata file lookup logic

Update ConfigurationMetadataAnnotationProcessor to find the additional
metadata json file using createResource rather than getResource. Prior
to this commit the file could be skipped when multiple files were
contained on the classpath.

Fixes gh-2271

spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/ConfigurationMetadataAnnotationProcessor.java

@@ -343,14 +343,10 @@ public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor
 
 	private ConfigurationMetadata mergeManualMetadata(ConfigurationMetadata metadata) {
 		try {
-			FileObject manualMetadata = this.processingEnv.getFiler().getResource(
-					StandardLocation.CLASS_PATH, "",
+			FileObject manualMetadata = this.processingEnv.getFiler().createResource(
+					StandardLocation.CLASS_OUTPUT, "",
 					"META-INF/additional-spring-configuration-metadata.json");
-			if (!"file".equals(manualMetadata.toUri().getScheme())) {
-				// We only want local files, not any classpath jars
-				return metadata;
-			}
-			InputStream inputStream = manualMetadata.openInputStream();
+			InputStream inputStream = manualMetadata.toUri().toURL().openStream();
 			try {
 				ConfigurationMetadata merged = new ConfigurationMetadata(metadata);
 				try {