etc/options

--- a/etc/options	Wed Jul 19 11:31:19 2023 +0200
+++ b/etc/options	Wed Jul 19 11:40:00 2023 +0200
@@ -183,6 +183,9 @@
 
 section "Build Process"
 
+option build_context : string = ""
+  -- "free-form information for session build (to be interpreted in Isabelle/ML)"
+
 option build_thorough : bool = false
   -- "observe dependencies on options with tag 'content' or 'document'"