WIP: support a jlink'ed schnorr-example

This works on macOS if `gradle jlink` is followed by:

cp /nix/store/<hash>-secp256k1-0.6.0/lib/libsecp256k1.* \
   secp-examples-java/build/image/lib/

Author: msgilligan

build.gradle

@@ -1,5 +1,6 @@
 plugins {
     id 'com.github.hierynomus.license'      version '0.16.1' apply false
+    id 'org.beryx.jlink'                    version '3.1.4-rc' apply false
 }
 
 // Projects to be published with maven-publish

secp-examples-java/build.gradle

@@ -1,6 +1,7 @@
 plugins {
     id 'java'
     id 'application'
+    id 'org.beryx.jlink'    version '3.1.4-rc'
 }
 
 ext.moduleName = 'org.bitcoinj.secp.examples'
@@ -41,6 +42,13 @@ configurations {
     nativeToolRuntimeOnly.extendsFrom runtimeOnly
 }
 
+jlink {
+    options = ['--add-modules', 'org.bitcoinj.secp.ffm']
+    launcher {
+        name = application.applicationName
+    }
+}
+
 tasks.register('runEcdsa', JavaExec) {
     javaLauncher = javaToolchains.launcherFor {
         languageVersion = JavaLanguageVersion.of(javaToolchainVersion)