[Gradle] Fix build finished hooks on ci when using configuration cache (

elastic#116888)

Fixes two incompatibilities with Gradle configuration cache in our build scan build finished hook:

referencing static methods from build script
referencing gradle object from closure

build-tools-internal/src/main/groovy/elasticsearch.build-scan.gradle

@@ -12,10 +12,14 @@ import java.time.LocalDateTime;
 
 import org.elasticsearch.gradle.Architecture
 import org.elasticsearch.gradle.OS
+import static org.elasticsearch.gradle.internal.util.CiUtils.safeName
 
 import java.lang.management.ManagementFactory
 import java.time.LocalDateTime
 
+// Resolving this early to avoid issues with the build scan plugin in combination with the configuration cache usage
+def taskNames = gradle.startParameter.taskNames.join(' ')
+
 develocity {
 
   buildScan {
@@ -110,7 +114,7 @@ develocity {
 
             // Add a build annotation
             // See: https://buildkite.com/docs/agent/v3/cli-annotate
-            def body = """<div class="mb3"><span class="p1 border rounded">${System.getenv('BUILDKITE_LABEL')}</span> :gradle: ${result.failures ? 'failed' : 'successful'} build: <a href="${scan.buildScanUri}"><code>gradle ${gradle.startParameter.taskNames.join(' ')}</code></a></div>"""
+            def body = """<div class="mb3"><span class="p1 border rounded">${System.getenv('BUILDKITE_LABEL')}</span> :gradle: ${result.failures ? 'failed' : 'successful'} build: <a href="${scan.buildScanUri}"><code>gradle ${taskNames}</code></a></div>"""
             def process = [
               'buildkite-agent',
               'annotate',
@@ -131,7 +135,3 @@ develocity {
     }
   }
 }
-
-static def safeName(String string) {
-  return string.replaceAll(/[^a-zA-Z0-9_\-\.]+/, ' ').trim().replaceAll(' ', '_').toLowerCase()
-}

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/util/CiUtils.java

@@ -0,0 +1,18 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.gradle.internal.util;
+
+public class CiUtils {
+
+    static String safeName(String input) {
+        return input.replaceAll("[^a-zA-Z0-9_\\-\\.]+", " ").trim().replaceAll(" ", "_").toLowerCase();
+    }
+
+}