select/config_setting for clang-cl being ignored

When enabling a CI build using clang-cl.exe, I found that I needed to suppress a warning, but couldn't work out how to do this in the BUILD file.

I added a config_setting() and select() that should pick up the clang-cl configuration and pass -Wno-macro-redefined, but the flag is not passed to clang-cl.exe.

config_setting(
    name = "windows-clang-cl",
    constraint_values = [
        "@platforms//os:windows",
        "@bazel_tools//tools/cpp:clang-cl",
    ],
)

cc_library(
    [...]
    copts =
        select({
            # this should be used:
            ":windows-clang-cl": common_copts + windows_only_copts + ["-Wno-macro-redefined"],
            # but this is actually used:
            "@bazel_tools//src/conditions:windows": common_copts + windows_only_copts,
        }),
)

Links: commit, buildkite log. I'm using --incompatible_enable_cc_toolchain_resolution as recommended by the docs.

I believe that :windows-clang-cl is a strict subset of @bazel_tools//src/conditions:windows so I don't see why that branch of the select() is being ignored. What am I missing?