Traverse CrateGroupInfo when gathering CcInfo linking_context entries for use_cc_common_link

This fixes rust_library_group and rust_prost_library for experimental_use_cc_common_link

Author: ObsidianMinor

rust/private/rustc.bzl

@@ -1580,9 +1580,12 @@ def rustc_compile_action(
             toolchain.stdlib_linkflags.linking_context,
         ]
 
-        for dep in crate_info.deps.to_list():
-            if dep.cc_info:
-                linking_contexts.append(dep.cc_info.linking_context)
+        linking_contexts += [
+            ddep.cc_info.linking_context
+            for dep in crate_info.deps.to_list()
+            for ddep in (dep.crate_group_info.dep_variant_infos.to_list() if dep.crate_group_info else [dep])
+            if ddep.cc_info
+        ]
 
         # In the cc_common.link action we need to pass the name of the final
         # binary (output) relative to the package of this target.