[Gradle, JS] Add verbose option to yarn in debug mode

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/yarn/YarnBasics.kt

@@ -29,7 +29,9 @@ abstract class YarnBasics : NpmApi {
 
         project.execWithProgress(description) { exec ->
             exec.executable = nodeJsEnv.nodeExecutable
-            exec.args = listOf(yarnEnv.home.resolve("bin/yarn.js").absolutePath) + args
+            exec.args = listOf(yarnEnv.home.resolve("bin/yarn.js").absolutePath) +
+                    args +
+                    if (project.logger.isDebugEnabled) "--verbose" else ""
             exec.workingDir = dir
         }
     }