diff --git a/src/Pure/Admin/build_zstd.scala b/src/Pure/Admin/build_zstd.scala
--- a/src/Pure/Admin/build_zstd.scala
+++ b/src/Pure/Admin/build_zstd.scala
@@ -1,119 +1,119 @@
 /*  Title:      Pure/Admin/build_zstd.scala
     Author:     Makarius
 
 Build Isabelle zstd-jni component from official download.
 */
 
 package isabelle
 
 
 object Build_Zstd {
   /* platforms */
 
-  sealed case class Platform(name: String, template: String, exe: Boolean = false) {
+  sealed case class Platform_Info(name: String, template: String, exe: Boolean = false) {
     def install(jar_dir: Path, component_dir: Path, version: String): Unit = {
       val source = jar_dir + Path.explode(template.replace("{V}", version))
       val target = Isabelle_System.make_directory(component_dir + Path.basic(name))
       Isabelle_System.copy_file(source, target)
       if (exe) File.set_executable(target + source.base, true)
     }
   }
 
   private val platforms =
     List(
-      Platform("arm64-darwin", "darwin/aarch64/libzstd-jni-{V}.dylib"),
-      Platform("x86_64-darwin", "darwin/x86_64/libzstd-jni-{V}.dylib"),
-      Platform("arm64-linux", "linux/aarch64/libzstd-jni-{V}.so"),
-      Platform("x86_64-linux", "linux/amd64/libzstd-jni-{V}.so"),
-      Platform("x86_64-windows", "win/amd64/libzstd-jni-{V}.dll", exe = true))
+      Platform_Info("arm64-darwin", "darwin/aarch64/libzstd-jni-{V}.dylib"),
+      Platform_Info("x86_64-darwin", "darwin/x86_64/libzstd-jni-{V}.dylib"),
+      Platform_Info("arm64-linux", "linux/aarch64/libzstd-jni-{V}.so"),
+      Platform_Info("x86_64-linux", "linux/amd64/libzstd-jni-{V}.so"),
+      Platform_Info("x86_64-windows", "win/amd64/libzstd-jni-{V}.dll", exe = true))
 
 
   /* build zstd */
 
   val license_url = "https://raw.githubusercontent.com/luben/zstd-jni/master/LICENSE"
   val default_download_url = "https://repo1.maven.org/maven2/com/github/luben/zstd-jni"
   val default_version = "1.5.2-5"
 
   def build_zstd(
     target_dir: Path = Path.current,
     download_url: String = default_download_url,
     version: String = default_version,
     progress: Progress = new Progress,
   ): Unit = {
     /* component */
 
     val component_name = "zstd-jni-" + version
     val component_dir = Isabelle_System.new_directory(target_dir + Path.basic(component_name))
     progress.echo("Component " + component_dir)
 
     File.write(component_dir + Path.basic("README"),
       "This is " + component_name + " from\n" + download_url +
         "\n\n        Makarius\n        " + Date.Format.date(Date.now()) + "\n")
 
     Isabelle_System.download_file(
       license_url, component_dir + Path.basic("LICENSE"), progress = progress)
 
 
     /* jar */
 
     val jar_name = component_name + ".jar"
     val jar = component_dir + Path.basic(jar_name)
     Isabelle_System.download_file(
       download_url + "/" + version + "/" + jar_name, jar, progress = progress)
 
     Isabelle_System.with_tmp_dir("build") { jar_dir =>
       progress.echo("Unpacking " + jar)
       Isabelle_System.bash("isabelle_jdk jar xf " + File.bash_path(jar.absolute),
         cwd = jar_dir.file).check
       for (platform <- platforms) platform.install(jar_dir, component_dir, version)
     }
 
 
     /* settings */
 
     val etc_dir = Isabelle_System.make_directory(component_dir + Path.basic("etc"))
 
     File.write(etc_dir + Path.basic("settings"),
 """# -*- shell-script -*- :mode=shellscript:
 
 ISABELLE_ZSTD_HOME="$COMPONENT"
 
 classpath "$ISABELLE_ZSTD_HOME/""" + jar_name + """"
 """)
   }
 
 
   /* Isabelle tool wrapper */
 
   val isabelle_tool =
     Isabelle_Tool("build_zstd", "build Isabelle zstd-jni component from official download",
       Scala_Project.here,
       { args =>
         var target_dir = Path.current
         var download_url = default_download_url
         var version = default_version
 
         val getopts = Getopts("""
 Usage: isabelle build_zstd [OPTIONS]
 
   Options are:
     -D DIR       target directory (default ".")
     -U URL       download URL (default: """ + quote(default_download_url) + """)
     -V VERSION   version (default: """ + quote(default_version) + """)
 
   Build zstd-jni component from the specified download base URL and VERSION,
   see also https://github.com/luben/zstd-jni
 """,
           "D:" -> (arg => target_dir = Path.explode(arg)),
           "U:" -> (arg => download_url = arg),
           "V:" -> (arg => version = arg))
 
         val more_args = getopts(args)
         if (more_args.nonEmpty) getopts.usage()
 
         val progress = new Console_Progress()
 
         build_zstd(target_dir = target_dir, download_url = download_url,
           version = version, progress = progress)
       })
 }