[Gradle, JS] Add check on run and dist task

- Check existence of compile output file to prevent fail in case of NO-SOURCE

#KT-31894 fixed

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/nodejs/NodeJsExec.kt

@@ -22,6 +22,13 @@ open class NodeJsExec : AbstractExecTask<NodeJsExec>(NodeJsExec::class.java), Re
     @get:Internal
     override lateinit var compilation: KotlinJsCompilation
 
+    init {
+        onlyIf {
+            compilation.compileKotlinTask.outputFile
+                .exists()
+        }
+    }
+
     @Input
     var sourceMapStackTraces = true
 

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/webpack/KotlinWebpack.kt

@@ -56,6 +56,12 @@ open class KotlinWebpack : DefaultTask(), RequiresNpmDependencies {
     var entry: File? = null
         get() = field ?: compilation.compileKotlinTask.outputFile
 
+    init {
+        onlyIf {
+            entry!!.exists()
+        }
+    }
+
     @get:Internal
     internal var resolveFromModulesFirst: Boolean = false