Allow targetting Alpine Linux independently of regular Linux when dow…

…nloading Adoptium/Eclipse Temurin builds

Adoptium now publish validated Alpine Linux builds of Eclipse Temurin JVM, compiled directly against musl libc (rather than glibc). Using these would avoid the need to use the Alpine GLIBC package which is not recommended by the Alpine team, and which is no longer supported by Adopt in their own containers. See the long discussion at adoptium/containers#1

At time of writing we cannot move away from glibc because the Tanuki wrapper does not seem to work against musl, OR with either gcompat or libc6-compat compatibility layers (both seem to be missing some symbols). However this allows us to do so in future by changing the targetted `OperatingSystem` in the alpine and docker-dind `Distro`s

buildSrc/src/main/groovy/com/thoughtworks/go/build/AdoptiumUrlHelper.groovy

@@ -16,22 +16,13 @@
 
 package com.thoughtworks.go.build
 
-enum OperatingSystem {
-  windows("zip"), linux("tar.gz"), mac("tar.gz")
-
-  final String extension
-
-  OperatingSystem(String extension) {
-    this.extension = extension
-  }
-}
 
 class AdoptiumUrlHelper {
   static String downloadURL(OperatingSystem operatingSystem, Integer featureVersion, Integer interimVersion, Integer updateVersion, Integer buildVersion) {
     String versionComponent = [featureVersion, interimVersion, updateVersion].findAll({ it != null }).join('.')
     String featureSuffix = updateVersion == null ? '' : 'U'
 
-    "https://github.com/adoptium/temurin${featureVersion}-binaries/releases/download/jdk-${versionComponent}%2B${buildVersion}/OpenJDK${featureVersion}${featureSuffix}-jre_x64_${operatingSystem.name()}_hotspot_${versionComponent}_${buildVersion}.${operatingSystem.extension}"
+    "https://github.com/adoptium/temurin${featureVersion}-binaries/releases/download/jdk-${versionComponent}%2B${buildVersion}/OpenJDK${featureVersion}${featureSuffix}-jre_x64_${operatingSystem.adoptiumAlias()}_hotspot_${versionComponent}_${buildVersion}.${operatingSystem.extension}"
   }
 
   static String sha256sumURL(OperatingSystem operatingSystem, Integer featureVersion, Integer interimVersion, Integer updateVersion, Integer buildVersion) {

buildSrc/src/main/groovy/com/thoughtworks/go/build/OperatingSystem.groovy

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2021 ThoughtWorks, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.thoughtworks.go.build
+
+enum OperatingSystem {
+  windows("zip"), linux("tar.gz"), alpine_linux("tar.gz"), mac("tar.gz")
+
+  final String extension
+
+  OperatingSystem(String extension) {
+    this.extension = extension
+  }
+
+  String adoptiumAlias() {
+    name().replace('_', '-')
+  }
+}

buildSrc/src/main/groovy/com/thoughtworks/go/build/docker/Distro.groovy

@@ -16,11 +16,17 @@
 
 package com.thoughtworks.go.build.docker
 
+import com.thoughtworks.go.build.OperatingSystem
 import org.gradle.api.Project
 
 enum Distro implements DistroBehavior {
 
   alpine{
+    @Override
+    OperatingSystem getOperatingSystem() {
+      OperatingSystem.linux
+    }
+
     @Override
     List<DistroVersion> getSupportedVersions() {
       def installSasl_Post_3_9 = ['apk add --no-cache libsasl']
@@ -183,6 +189,11 @@ enum Distro implements DistroBehavior {
   },
 
   docker{
+    @Override
+    OperatingSystem getOperatingSystem() {
+      return alpine.getOperatingSystem()
+    }
+
     @Override
     boolean isPrivilegedModeSupport() {
       return true
@@ -212,7 +223,6 @@ enum Distro implements DistroBehavior {
       return alpine.getInstallPrerequisitesCommands(distroVersion)
     }
 
-
     @Override
     List<String> getInstallJavaCommands(Project project) {
       return alpine.getInstallJavaCommands(project)

buildSrc/src/main/groovy/com/thoughtworks/go/build/docker/DistroBehavior.groovy

@@ -17,6 +17,7 @@
 package com.thoughtworks.go.build.docker
 
 import com.thoughtworks.go.build.AdoptiumUrlHelper
+import com.thoughtworks.go.build.OperatingSystem
 import org.gradle.api.Project
 
 trait DistroBehavior {
@@ -54,7 +55,7 @@ trait DistroBehavior {
 
   List<String> getInstallJavaCommands(Project project) {
     def downloadUrl = AdoptiumUrlHelper.downloadURL(
-      com.thoughtworks.go.build.OperatingSystem.linux,
+      getOperatingSystem(),
       project.packaging.adoptOpenjdk.featureVersion,
       project.packaging.adoptOpenjdk.interimVersion,
       project.packaging.adoptOpenjdk.updateVersion,
@@ -68,6 +69,10 @@ trait DistroBehavior {
     ]
   }
 
+  OperatingSystem getOperatingSystem() {
+    OperatingSystem.linux
+  }
+
   Map<String, String> getEnvironmentVariables(DistroVersion distroVersion) {
     return [GO_JAVA_HOME: '/gocd-jre']
   }