Fix cc_shared_library to take into account unused CcInfos

In
f9008f6
cc_shared_library was fixed to make sure that indirect top level deps were
wrapped in "alwayslink" and not dropped by the linker.

The loop which finds them didn't check for previously visited nodes under the
assumption that it'd be quick to exit because a top level dep containing code
would be found a few levels into the dependencies. This causes the code to hang
in builds where there are custom C++ rules that do not propagate all the
CcInfos from their deps.

The code works using the structure of the graph recreated by the aspect, if it
sees a target providing a dependency which isn't part of the static linker
inputs, it assumes that it's an empty top level dependency and therefore we
have to keep crawling up the graph to find the library that needs to be
whole-archived. What was happening though was that the custom C++ rule cut off
that dependency (even though it had code to link) and didn't make it part of
the CcInfo it provided. The code would go many levels down and would revisit
the same nodes over and over.

RELNOTES:none
PiperOrigin-RevId: 521717764
Change-Id: I0935ceb53572d6000d86cde518a6759b95c956a5

src/main/starlark/builtins_bzl/common/cc/experimental_cc_shared_library.bzl

@@ -270,14 +270,17 @@ def _find_top_level_linker_input_labels(
     top_level_linker_input_labels_set = {}
     nodes_to_check = list(nodes)
 
+    seen_nodes_set = {}
     for i in range(2147483647):
         if i == len(nodes_to_check):
             break
 
         node = nodes_to_check[i]
         must_add_children = False
+        node_str_owners = []
         for owner in node.owners:
             owner_str = str(owner)
+            node_str_owners.append(owner_str)
             if owner_str in linker_inputs_to_be_linked_statically_map:
                 must_add_children = True
                 for linker_input in linker_inputs_to_be_linked_statically_map[owner_str]:
@@ -290,8 +293,10 @@ def _find_top_level_linker_input_labels(
                 # linker_inputs but didn't contribute any linker_input of its own.
                 must_add_children = True
 
-        if must_add_children:
+        node_key = "".join(node_str_owners)
+        if must_add_children and node_key not in seen_nodes_set:
             nodes_to_check.extend(node.children)
+            seen_nodes_set[node_key] = True
 
     return top_level_linker_input_labels_set