Freeze libraries to link before interning them.

Otherwise, Blaze is susceptible to a race condition:

1. Node A creates a list ["x"] and interns it
2. Node B creates the same list ["x"] and interns it; it gets back a still mutable reference to the list created by node A
3. Node B finishes, freezes its Starlark data structures and puts a reference to the list (which is secretly created by Node A) into a provider
4. Node A adds "y" to the list
5. Now Node C (depending on Node B) will observe the values of the list as ["x", "y"], even though that's totally not what Node B intended

RELNOTES: None.
PiperOrigin-RevId: 947612088
Change-Id: I98fd1dadaaa0e0677577627ce63039599a72f66b

cc/private/link/create_libraries_to_link_values.bzl

diff --git a/cc/private/link/create_libraries_to_link_values.bzl b/cc/private/link/create_libraries_to_link_values.bzl
index fa02879..0822758 100644
--- a/cc/private/link/create_libraries_to_link_values.bzl
+++ b/cc/private/link/create_libraries_to_link_values.bzl
@@ -14,6 +14,7 @@
 """Goes over LibraryToLinks and produces LibraryToLinkValue-s."""
 
 load("//cc/common:cc_helper_internal.bzl", "is_shared_library", "is_versioned_shared_library", "root_relative_path")
+load("//cc/private:cc_internal.bzl", _cc_internal = "cc_internal")
 
 # Types of LibraryToLinkValues
 _TYPE = struct(
@@ -58,7 +59,7 @@
             libraries_to_link_values.append(
                 _ObjectFileGroupInfo(
                     type = _TYPE.OBJECT_FILE_GROUP,
-                    object_files = [object_file],
+                    object_files = _cc_internal.freeze([object_file]),
                     is_whole_archive = False,
                 ),
             )
@@ -225,7 +226,7 @@
                     libraries_to_link_values.append(
                         _ObjectFileGroupInfo(
                             type = _TYPE.OBJECT_FILE_GROUP,
-                            object_files = [object],
+                            object_files = _cc_internal.freeze([object]),
                             is_whole_archive = True,
                         ),
                     )
@@ -244,7 +245,7 @@
             libraries_to_link_values.append(
                 _ObjectFileGroupInfo(
                     type = _TYPE.OBJECT_FILE_GROUP,
-                    object_files = objects,
+                    object_files = _cc_internal.freeze(objects),
                     is_whole_archive = False,
                 ),
             )