Using javac to generate header

jni/android/build.gradle.kts

@@ -0,0 +1,48 @@
+plugins {
+    id("com.android.library")
+    kotlin("android")
+}
+
+kotlin {
+    explicitApi()
+}
+
+dependencies {
+    api(project(":jni"))
+    implementation(kotlin("stdlib-jdk8"))
+}
+
+android {
+    defaultConfig {
+        compileSdkVersion(30)
+        minSdkVersion(21)
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+        externalNativeBuild {
+            cmake {}
+        }
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_1_8
+        targetCompatibility = JavaVersion.VERSION_1_8
+    }
+
+    externalNativeBuild {
+        cmake {
+            setPath("src/main/CMakeLists.txt")
+        }
+    }
+    ndkVersion = "21.3.6528147"
+
+    afterEvaluate {
+        tasks.withType<com.android.build.gradle.tasks.factory.AndroidUnitTest>().all {
+            enabled = false
+        }
+    }
+}
+
+afterEvaluate {
+    configure(listOf("Debug", "Release").map { tasks["externalNativeBuild$it"] }) {
+        dependsOn(":native:buildSecp256k1Android")
+    }
+}