Add test on yarn downloading non-default version

- Previously we skipped yarn setup, if yarn folder exists, not paying attention on what concrete yarn version installed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kotlin2JsGradlePluginIT.kt

@@ -432,5 +432,16 @@ class Kotlin2JsGradlePluginIT : BaseGradleIT() {
                 ":yarnFolderCheck"
             )
         }
+
+        gradleBuildScript().appendText("\nyarn.version = \"1.9.3\"")
+
+        build("yarnConcreteVersionFolderChecker") {
+            assertSuccessful()
+
+            assertTasksExecuted(
+                ":kotlinYarnSetup",
+                ":yarnConcreteVersionFolderChecker"
+            )
+        }
     }
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/yarn-setup/build.gradle.kts

@@ -1,3 +1,4 @@
+import org.jetbrains.kotlin.gradle.targets.js.yarn.YarnSetupTask
 import org.jetbrains.kotlin.gradle.targets.js.yarn.yarn
 
 plugins {
@@ -30,6 +31,16 @@ tasks {
             }
         }
     }
+
+    val yarnConcreteVersionFolderChecker by registering {
+        dependsOn(getByName("kotlinYarnSetup"))
+
+        doLast {
+            if (!yarn.installationDir.resolve("yarn-v1.9.3").exists()) {
+                throw GradleException()
+            }
+        }
+    }
 }
 
 kotlin.sourceSets {