automatically use toolchain if on right platform or download otherwise

[Vampire]

I envision some convenient and declarative way to express what the subject says.
What I have currently is

val isWindows = Os.isFamily(FAMILY_WINDOWS)
val isLinux = Os.isFamily(FAMILY_UNIX)
if (isWindows || isLinux) {
    targetPlatform(if (isWindows) "windows" else "linux") {
        setJdkHome(javaToolchains.launcherFor(java.toolchain).get().executablePath.asFile.parentFile.parentFile)
    }
}
if (!version.toString().endsWith("-SNAPSHOT")) {
    if (!isWindows) {
        targetPlatform("windows") {
            setJdkHome(jdkDownload("https://github.com/adoptium/temurin17-binaries/releases/download/jdk-17.0.1%2B12/OpenJDK17U-jdk_x64_windows_hotspot_17.0.1_12.zip"))
        }
    }
    if (!isLinux) {
        targetPlatform("linux") {
            setJdkHome(jdkDownload("https://github.com/adoptium/temurin17-binaries/releases/download/jdk-17.0.1%2B12/OpenJDK17U-jdk_x64_linux_hotspot_17.0.1_12.tar.gz"))
        }
    }
}

so that I can test using runtime task without the need to download either JDK (will report a different issue about that) and when releasing the JDK for the other platform is downloaded.