Exclude generated files from formatting

Author: jjohannes

src/main/java/org/gradlex/conventions/check/SpotlessConventionsPlugin.java

@@ -42,10 +42,12 @@ public void apply(Project project) {
 
         // format the source code
         spotless.java(java -> {
+            java.targetExclude("build/**");
             java.palantirJavaFormat();
             java.licenseHeader("// SPDX-License-Identifier: Apache-2.0\n", "package|import");
         });
         spotless.format("javaPackageInfoFiles", java -> {
+            java.targetExclude("build/**");
             // add a separate extension due to https://github.com/diffplug/spotless/issues/532
             java.target("src/**/package-info.java");