Avoid running configure when plugins/ modified

We use an indirection, producing the sorted list of subdirectories of
plugins/, so that dune can recognize it hasn't changed and doesn't
rerun configure. Since configure regenerates a timestamp this avoids
recompiling the stdlib.

Fix #12750.

1 files changed, 10 insertions, 0 deletions

diff --git a/config/list_plugins.ml b/config/list_plugins.ml
new file mode 100644
index 0000000000..5e2827bfe0
--- /dev/null
+++ b/config/list_plugins.ml
@@ -0,0 +1,10 @@
+let plugins =
+  try Sys.readdir "plugins"
+  with _ -> [||]
+
+let () = Array.sort compare plugins
+
+let () =Array.iter (fun f ->
+    let f' = "plugins/"^f in
+    if Sys.is_directory f' && f.[0] <> '.' then print_endline f)
+    plugins