mbed-os/tools/test/config/feature_remove/targets.json

{
    "test_target": {
        "supported_toolchains": ["GCC_ARM"],
        "core": "Cortex-M0",
        "extra_labels": [],
        "features": ["BOOTLOADER"],
        "c_lib": "std",
        "supported_c_libs": {
                "arm": ["std"],
                "gcc_arm": ["std", "small"],
                "iar": ["std"]
        }
    }
}