Fix printing internal libs with the command "dune describe external-lib-deps"

bin/describe.ml

@@ -719,9 +719,10 @@ module External_lib_deps = struct
   let external_resolved_libs setup super_context =
     let open Memo.O in
     let context = Super_context.context super_context in
-    let* public_libs = Scope.DB.public_libs context in
+    let* scope = Scope.DB.find_by_dir context.build_dir in
+    let db = Scope.libs scope in
     let* libs = libs context setup in
-    external_lib_deps public_libs libs
+    external_lib_deps db libs
 
   let to_dyn context_name external_resolved_libs =
     Dyn.Tuple

test/blackbox-tests/test-cases/external-lib-deps/exclude-internal-deps.t/dune

@@ -0,0 +1,3 @@
+(library
+ (name foo)
+ (libraries inter_lib a))

test/blackbox-tests/test-cases/external-lib-deps/exclude-internal-deps.t/dune-project

@@ -0,0 +1,3 @@
+(lang dune 1.9)
+(name foo)
+(allow_approximate_merlin true)

test/blackbox-tests/test-cases/external-lib-deps/exclude-internal-deps.t/lib/dune

@@ -0,0 +1,3 @@
+(library
+ (name inter_lib)
+ (libraries a))

test/blackbox-tests/test-cases/external-lib-deps/exclude-internal-deps.t/run.t

@@ -0,0 +1,8 @@
+Expected: The dependency "inter_lib" in ./dune file was printed, the "inter_lib" lib is already
+an internal lib that declared in ./lib/dune file. The command "dune describe external-lib-deps"
+print only the external libraries by dir.
+
+  $ dune describe external-lib-deps
+  (default
+   ((. ((a required)))
+    (lib ((a required)))))