Support debug build configuration for K/N

[fzhinkin]

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Currently, kotlinx-benchmark implicitly use release configuration for K/N builds. That's absolutely sane and reasonable default. However, in some cases (like this), performance need to be collected and validated for debug builds.

It would be nice to have an option to choose K/N build configuration, with release still being a default.

[fzhinkin]

Probably, the build configuration could be configured when a benchmarking target is declared. Something like this:

benchmark {
    targets {
        register("macosArm64") {
             this as NativeBenchmarkTarget
             buildType = NativeBuildType.DEBUG
             // or simply, debug = true
        }
    }
}