switched build system from sbt to Gradle

antlr/build.gradle

@@ -0,0 +1,19 @@
+plugins {
+    id 'antlr'
+}
+
+dependencies {
+    implementation rootProject
+
+    testImplementation group: "net.woggioni", name: "jwo", version: getProperty('version.jwo')
+    testImplementation project(':test-utils')
+    testImplementation group: "com.fasterxml.jackson.core", name:"jackson-databind", version: getProperty('version.jackson')
+    testImplementation group: "org.tukaani", name: "xz", version: getProperty('version.xz')
+    antlr group: "org.antlr", name: "antlr4", version: getProperty('version.antlr')
+    antlr group: "org.antlr", name: "antlr4-runtime", version: getProperty('version.antlr')
+}
+
+generateGrammarSource {
+    maxHeapSize = "64m"
+    arguments += ['-package', 'net.woggioni.wson.antlr']
+}