add build log format for managed builds;

--- a/src/Pure/Admin/build_log.scala	Mon Jun 10 17:08:47 2024 +0200
+++ b/src/Pure/Admin/build_log.scala	Mon Jun 10 18:45:12 2024 +0200
@@ -342,6 +342,15 @@
     val BUILD = "=== BUILD ==="
   }
 
+  object Build_Manager {
+    val log_prefix = "build_manager"
+    val engine = "build_manager"
+    val Start = new Regex("""^Starting job \S+ at ([^,]+), on (\S+)$""")
+    val End = new Regex("""^Job ended at ([^,]+), with status \w+$""")
+    val Isabelle_Version = List(new Regex("""^Using Isabelle/(\w+)$"""))
+    val AFP_Version = List(new Regex("""^Using AFP/(\w+)$"""))
+  }
+
   private def parse_meta_info(log_file: Log_File): Meta_Info = {
     def parse(engine: String, host: String, start: Date,
       End: Regex, Isabelle_Version: List[Regex], AFP_Version: List[Regex]
@@ -391,6 +400,10 @@
         parse(AFP_Test.engine, "", start, AFP_Test.End,
           AFP_Test.Isabelle_Version, AFP_Test.AFP_Version)
 
+      case Build_Manager.Start(log_file.Strict_Date(start), host) :: _ =>
+        parse(Build_Manager.engine, host, start, Build_Manager.End,
+          Build_Manager.Isabelle_Version, Build_Manager.AFP_Version)
+
       case line :: _ if line.startsWith("\u0000") => Meta_Info.empty
       case List(Isatest.End(_)) => Meta_Info.empty
       case _ :: AFP_Test.Bad_Init() :: _ => Meta_Info.empty