rust_doc_test error when crate has transitive cc_library dependencies

[UebelAndre]

I'm getting this error trying to use rust_doc_test on 1fc2993

Traceback (most recent call last):
	File "/private/var/tmp/_bazel_user/c4900dc498759a5aae30fdfe5c69c114/external/rules_rust/rust/private/rustdoc_test.bzl", line 44, column 33, in _rust_doc_test_impl
		flags = _build_rustdoc_flags(dep_info, crate_info)
	File "/private/var/tmp/_bazel_user/c4900dc498759a5aae30fdfe5c69c114/external/rules_rust/rust/private/rustdoc_test.bzl", line 108, column 37, in _build_rustdoc_flags
		is_static = bool(lib_to_link.static_library or lib_to_link.pic_static_library)
Error: 'LinkerInput' value has no field or method 'static_library'

The target I'm using rust_doc_test on transitive cc_library dependencies which I suspect is the cause of the issue here.

The issue can be reproduced with the following diff to rules_rust:

diff --git a/examples/bindgen/BUILD.bazel b/examples/bindgen/BUILD.bazel
index 8e36e20..e4aede4 100644
--- a/examples/bindgen/BUILD.bazel
+++ b/examples/bindgen/BUILD.bazel
@@ -1,6 +1,6 @@
 load("@rules_cc//cc:defs.bzl", "cc_library")
 load("@rules_rust//bindgen:bindgen.bzl", "rust_bindgen_library")
-load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_test")
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_test", "rust_doc_test")

 cc_library(
     name = "simple",
@@ -26,3 +26,8 @@ rust_test(
     name = "simple_test",
     crate = ":simple_example",
 )
+
+rust_doc_test(
+    name = "doc_test",
+    crate = ":simple_example",
+)