Move jflex download out from update_dependencies, add lexer (ant) tasks to frontend project

compiler/frontend/build.gradle.kts

@@ -3,6 +3,8 @@ apply { plugin("kotlin") }
 
 jvmTarget = "1.6"
 
+val jflexPath by configurations.creating
+
 dependencies {
     compile(project(":core:descriptors"))
     compile(project(":core:deserialization"))
@@ -11,9 +13,15 @@ dependencies {
     compile(project(":compiler:resolution"))
     compile(projectDist(":kotlin-script-runtime"))
     compile(commonDep("io.javaslang","javaslang"))
+    jflexPath(commonDep("org.jetbrains.intellij.deps.jflex", "jflex"))
 }
 
 sourceSets {
     "main" { projectDefault() }
     "test" {}
 }
+
+ant.importBuild("buildLexer.xml")
+
+ant.properties["builddir"] = buildDir.absolutePath
+ant.properties["flex.classpath"] = jflexPath.asPath