Explicitly add cuda and cxx features to cc_* rules

[dmadisetti]

Description of the feature request:

Native cuda support (#6578) is pretty close with clang. Things almost run out of the box with a properly configured clang toolchain. There's still a bit of friction since cuda and cpp share the same toolchain, there should be a near native way of distinguishing compilation types.

What underlying problem are you trying to solve with this feature?

Proposal, add features cxx and cuda in https://cs.opensource.google/bazel/bazel/+/master:tools/cpp/unix_cc_toolchain_config.bzl;l=218;drc=2fc2f4cac889919e80c7932e7933b281a1bce3e3

    default_compile_flags_feature = feature(
        name = "default_compile_flags",
        enabled = True,
        flag_sets = [
            # ... all the other features
            flag_set(
                actions = all_cpp_compile_actions + [ACTION_NAMES.lto_backend],
                flag_groups = ([
                    flag_group(
                        flags = ctx.attr.cxx_flags,
                    ),
                ] if ctx.attr.cxx_flags else []),
                with_features = [with_feature_set(features = ["cxx"])],
            ),
            flag_set(
                actions = all_cpp_compile_actions + [ACTION_NAMES.lto_backend],
                flag_groups = ([
                    flag_group(
                        flags = ctx.attr.cuda_flags,
                    ),
                ] if ctx.attr.cuda_flags else []),
                with_features = [with_feature_set(features = ["cuda"])],
            ),
        ],
    )

    cxx_feature = feature(name = "cxx", enabled = True)
    cuda_feature = feature(name = "cuda")

and then add the relevant attrs for toolchain use.

This will let users distinguish between cuda and cxxflags on the toolchain level. I don't think the flags need to be mutually exclusive. A second effort would to be document all these flags (see #8706 (comment))

Which operating system are you running Bazel on?

No response

What is the output of bazel info release?

No response

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse master; git rev-parse HEAD ?

2fc2f4cac889919e80c7932e7933b281a1bce3e3

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

This request comes from trying to resolve this issue: tweag/rules_nixpkgs#218 with a clang toolchain.

[github-actions]

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[github-actions]

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