lib/Tools/scala_build

--- a/lib/Tools/scala_build	Sun Jul 18 13:41:20 2021 +0200
+++ b/lib/Tools/scala_build	Sun Jul 18 21:46:16 2021 +0200
@@ -17,6 +17,9 @@
   echo "    -f           force fresh build"
   echo "    -q           quiet mode: suppress stdout/stderr"
   echo
+  echo "  Build Isabelle/Scala/Java modules of all registered components"
+  echo "  (if required)."
+  echo
   exit 1
 }