As far as I can tell there is no way to write a config_setting that expresses the constraint "the target operating system is Linux". You can write one for for Windows, or for Darwin. You can write one for the pair of constraints "the operating system is Linux and the processor architecture is x86-64". But you can't do it for Linux. This means every place you want to write a linux-specific select case, you must enumerate all the possible CPU architectures on which Linux runs, which is confusing, verbose, inconsistent, and fragile.