Android: Add very basic Curve25519 benchmarks

java/android/benchmarks/build.gradle

@@ -0,0 +1,38 @@
+plugins {
+    id 'com.android.library' version '7.0.0'
+    id 'androidx.benchmark' version '1.1.1'
+}
+
+repositories {
+    google()
+    mavenCentral()
+    mavenLocal()
+}
+
+android {
+    compileSdkVersion 31
+
+    defaultConfig {
+        minSdkVersion 19
+        targetSdkVersion 30
+        multiDexEnabled true
+    }
+
+    testBuildType "release"
+
+    compileOptions {
+        coreLibraryDesugaringEnabled true
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+
+    namespace "org.signal.libsignal.benchmarks"
+}
+
+dependencies {
+    androidTestImplementation "androidx.test:runner:1.4.0"
+    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
+    androidTestImplementation 'androidx.benchmark:benchmark-junit4:1.1.1'
+    coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.1.6'
+    androidTestImplementation project(':android')
+}