Add C++ runtime libs to cgo action inputs (#4594)

With @llvm toolchain, libc++ is provided via cc_toolchain's
`static_runtime_library`/`dynamic_runtime_library`. These groups should
be added to link actions otherwise cgo code that attempts to link libc++
will not work properly. It seems there were previous attempts to drop
libc++ - I'm not sure the best way to harmonize these, some tweaking of
this PR may be necessary. @jayconrod @fmeum wdyt?