Replace deprecated method getBuildDir()

See gh-31416

buildSrc/src/main/java/org/springframework/build/api/ApiDiffPlugin.java

@@ -131,7 +131,8 @@ public class ApiDiffPlugin implements Plugin<Project> {
 	}
 
 	private File getOutputFile(String baseLineVersion, Project project) {
-		Path outDir = Paths.get(project.getRootProject().getBuildDir().getAbsolutePath(),
+		Path outDir = Paths.get(project.getRootProject()
+						.getLayout().getBuildDirectory().getAsFile().get().getAbsolutePath(),
 				"reports", "api-diff",
 				baseLineVersion + "_to_" + project.getRootProject().getVersion());
 		return project.file(outDir.resolve(project.getName() + ".html").toString());

settings.gradle

@@ -47,7 +47,7 @@ rootProject.children.each {project ->
 settings.gradle.projectsLoaded {
 	gradleEnterprise {
 		buildScan {
-			File buildDir = settings.gradle.rootProject.getBuildDir()
+			File buildDir = settings.gradle.rootProject.getLayout().getBuildDirectory().getAsFile().get()
 			buildDir.mkdirs()
 			new File(buildDir, "build-scan-uri.txt").text = "(build scan not generated)"
 			buildScanPublished { scan ->