Prepare rust rules for Starlark CcToolchainInfo. (#2424)

#2425

Author: buildbreaker2021

rust/private/rustc.bzl

@@ -671,7 +671,15 @@ def collect_inputs(
     """
     linker_script = getattr(file, "linker_script") if hasattr(file, "linker_script") else None
 
-    linker_depset = cc_toolchain.linker_files()
+    # TODO: As of writing this comment Bazel used Java CcToolchainInfo.
+    # However there is ongoing work to rewrite provider in Starlark.
+    # rules_rust is not coupled with Bazel release. Remove conditional and change to
+    # _linker_files once Starlark CcToolchainInfo is visible to Bazel.
+    # https://github.com/bazelbuild/rules_rust/issues/2425
+    if hasattr(cc_toolchain, "_linker_files"):
+        linker_depset = cc_toolchain._linker_files
+    else:
+        linker_depset = cc_toolchain.linker_files()
     compilation_mode = ctx.var["COMPILATION_MODE"]
 
     use_pic = _should_use_pic(cc_toolchain, feature_configuration, crate_info.type, compilation_mode)