Build: fix the Elasticsearch download URL so it works on Linux (#725)

project/ElasticsearchPluginPlugin.scala

@@ -8,9 +8,9 @@ import java.util.zip.GZIPInputStream
 import scala.sys.process.Process
 
 /** SBT plugin providing functionality to run and build an Elasticsearch plugin. Also see:
-  * https://github.com/elastic/elasticsearch/blob/7ad3cf0d34/build-tools/src/main/java/org/elasticsearch/gradle/plugin/PluginBuildPlugin.java,
-  * build.sbt file in https://github.com/shikhar/eskka
-  */
+ * https://github.com/elastic/elasticsearch/blob/7ad3cf0d34/build-tools/src/main/java/org/elasticsearch/gradle/plugin/PluginBuildPlugin.java,
+ * build.sbt file in https://github.com/shikhar/eskka
+ */
 object ElasticsearchPluginPlugin extends AutoPlugin {
 
   override val trigger = noTrigger
@@ -132,7 +132,7 @@ object ElasticsearchPluginPlugin extends AutoPlugin {
     val log = sLog.value
     val elasticsearchVersionSuffix = {
       val osName = System.getProperty("os.name").toLowerCase()
-      val arch = System.getProperty("os.arch")
+      val arch = if (System.getProperty("os.arch") == "amd64") "x86_64" else System.getProperty("os.arch")
       if (osName.contains("mac")) s"darwin-$arch"
       else if (osName.contains("nix") || osName.contains("nux")) s"linux-$arch"
       else throw new RuntimeException(s"Unsupported operating system $osName, $arch")