feat(link): add additional_linker_inputs and link_output_dirs attrs

[Silvia-weka]

Two new attributes on runnable_attrs (d_binary, d_test):

additional_linker_inputs: label_list of files to make visible to the
link action's sandbox. Matches cc_library.additional_linker_inputs.
Already-supported use case: linker scripts referenced via
$(execpath ...) in linkopts. Now also: linker wrapper scripts
invoked via --ld-path=, and tools the wrapper itself spawns.

link_output_dirs: string_list of TreeArtifact directory names the
link action will produce in addition to the executable. Declared
in link_action via ctx.actions.declare_directory and (on the
cc_common.link path) passed to cc_common.link's additional_outputs,
so a linker wrapper can populate them and downstream rules can
consume them via DefaultInfo.files / a custom provider.

Plumbing:

• link_action now returns a struct(executable, additional_outputs). binary.bzl and test.bzl unpack and surface additional_outputs via DefaultInfo.files.
• link_with_d_action takes additional_outputs as a parameter and declares them on the action; LDC itself doesn't see them, they're purely for downstream consumption.
• linkopts now go through ctx.expand_location in compilation_action (against additional_linker_inputs), matching cc_library.linkopts semantics. The expanded form propagates via DInfo.linker_flags; link_action no longer adds ctx.attr.linkopts a second time (was a pre-existing double-add masked by the lack of expansion).