Bazel throws an error if the same dep appear in two select expressions

[jgao54]

Currently Bazel will throw an error while parsing a build file if it identifies the same dep appearing in two select expressions being added together.

I encountered this issue with the raze-generated BUILD.sha2-0.9.5.bazel file:

rust_library(
    name = "sha2",
    srcs = glob(["**/*.rs"]),
    aliases = {
    },
    crate_features = [
        "default",
        "std",
    ],
    crate_root = "src/lib.rs",
    data = [],
    edition = "2018",
    rustc_flags = [
        "--cap-lints=allow",
    ],
    tags = [
        "cargo-raze",
        "crate-name=sha2",
        "manual",
    ],
    version = "0.9.5",
    # buildifier: leave-alone
    deps = [
        "@raze__block_buffer__0_9_0//:block_buffer",
        "@raze__cfg_if__1_0_0//:cfg_if",
        "@raze__digest__0_9_0//:digest",
        "@raze__opaque_debug__0_3_0//:opaque_debug",
    ] + selects.with_or({
        # aarch64-apple-darwin
        (
            "@rules_rust//rust/platform:aarch64-apple-darwin",
        ): [
            "@raze__cpufeatures__0_1_4//:cpufeatures",
        ],
        "//conditions:default": [],
    }) + selects.with_or({
        # cfg(any(target_arch = "x86", target_arch = "x86_64"))
        (
            "@rules_rust//rust/platform:x86_64-apple-darwin",
            "@rules_rust//rust/platform:x86_64-unknown-linux-gnu",
        ): [
            "@raze__cpufeatures__0_1_4//:cpufeatures",
        ],
        "//conditions:default": [],
    }),
)

This will result in the following error during parsing of the build file:

ERROR: Label '@raze__cpufeatures__0_1_4//:cpufeatures' is duplicated in the 'deps' attribute of rule 'sha2'

[sayrer]

#512 should fix this.