How to avoid rebuilding while using bazel transitions to build multiple targets each with different configurations at once?

Question

I need to build multiple targets with one invocation each with different target architectures. I am using bazel transitions. It works as expected. When try to build the same targets individually with same configurations as specified in the command_line_option of bazel transitions, it starts rebuilding.

.bzl file is as follows:

def _impl(settings, attr):
    _ignore = (settings, attr)

    return {
        "Platform A": {
            "//command_line_option:platforms": "@local_config_platform//:host",
        },
        "Platform B": {
            "//command_line_option:platforms": "@external_repo//platforms:ccarm",
        },
    }

multi_arch_transition = transition(
    implementation = _impl,
    inputs = [],
    outputs = [
        "//command_line_option:platforms",
    ],
)

def _rule_impl(ctx):
    binary_a_platform_a = ctx.split_attr.binary_a["Platform A"]
    binary_b_platform_b = ctx.split_attr.binary_b["Platform B"]
    files = binary_a_platform_a.files.to_list() + binary_b_platform_b.files.to_list()

    return [DefaultInfo(
        files = depset(direct = files),
    )]

my_custom_multi_arch_rule = rule(
    implementation = _rule_impl,
    attrs = {
        "_allowlist_function_transition": attr.label(
            default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
        ),
        "binary_a": attr.label(cfg = multi_arch_transition),
        "binary_b": attr.label(cfg = multi_arch_transition),
    },
)

Build file is as follows:

cc_binary(
    name = "binary_platform_a",
    srcs = ["src/main.c"],
    deps = [
        "//libraries/myOtherLib:myotherlib",
    ],
)

cc_binary(
    name = "binary_platform_b",
    srcs = ["src/main.c"],
    deps = [
        "//libraries/myOtherLib:myotherlib",
    ],
)

my_custom_multi_arch_rule(
    name = "multiarch_build",
    binary_a = ":binary_platform_a",
    binary_b = ":binary_platform_b",
)

To build both binary targets (each configured with different architectures):

bazel build -s multiarch_build

It builds both binary targets as expected.

When I try to build an individual target again with the below command:

bazel build -s binary_platform_b --platforms=@external_repo//platforms:ccarm

It starts rebuilding. It does not use cached artefacts. It shows the below INFO

INFO: Build option --platforms has changed, discarding analysis cache.

I am expecting to use the artefacts from the actions of the target (multiarch_build)

How to avoid rebuilding? Here, platforms specified in transitions and in the command line to build individual targets are same. How it rebuilds and how to avoid? Where to change the code or other configurations to avoid rebuilding?