Generate native headers from kotlin file

Question

im trying to write JNI app and want to use kotlin in it.

As i understand kotlin equivalent of this:

private static native void hi();

is:

private external fun hi()

but the problemm is that i cant gen .h files with gradle in my project:

compileJava{
    options.headerOutputDirectory.set(file('src/main/java/idk/bluecross/JMM/natives'))
}

how can i do this?

here is my build.gradle by the way:

plugins {
    id 'java'
    id 'org.jetbrains.kotlin.jvm' version '1.8.0-RC2'
    id 'application'
    id 'cpp'
}

group 'idk.bluecross'
version '1.0-SNAPSHOT'
application.mainClass = 'idk.bluecross.example.Main'

application {
    applicationDefaultJvmArgs +=
            ["-Djava.library.path=" + file("${buildDir}/libs/jMM/shared").absolutePath]
}

compileJava{
    options.headerOutputDirectory.set(file('src/main/java/idk/bluecross/JMM/natives'))
}

repositories {
    mavenCentral()
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
}

model {
    platforms {
        x64 {
            architecture "x86_64"
        }
    }

    components {
        JMM(NativeLibrarySpec) {
            sources {
                cpp {
                    source {
                        srcDir "src/main/java/idk/bluecross/JMM/natives"
                    }
                }
            }
            targetPlatform "x64"
            binaries.all {
                def jvmHome = System.properties['java.home']
                if (targetPlatform.operatingSystem.macOsX) {
                    cppCompiler.args '-I', "${jvmHome}/include"
                    cppCompiler.args '-I', "${jvmHome}/include/darwin"
                    cppCompiler.args '-mmacosx-version-min=10.4'
                    linker.args '-mmacosx-version-min=10.4'
                } else if (targetPlatform.operatingSystem.linux) {
                    cppCompiler.args '-I', "${jvmHome}/include"
                    cppCompiler.args '-I', "${jvmHome}/include/linux"
                    cppCompiler.args '-D_FILE_OFFSET_BITS=64'
                } else if (targetPlatform.operatingSystem.windows) {
                    cppCompiler.args "-I${jvmHome}/include"
                    cppCompiler.args "-I${jvmHome}/include/win32"
                } else if (targetPlatform.operatingSystem.freeBSD) {
                    cppCompiler.args '-I', "${jvmHome}/include"
                    cppCompiler.args '-I', "${jvmHome}/include/freebsd"
                }
            }
        }
    }
}

classes.dependsOn 'JMMSharedLibrary'