Update bootstrap

New compiler arguments needed to publish JS IR libraries:
    - stdlib
    - kotlin-test

build.gradle.kts

@@ -8,7 +8,7 @@ buildscript {
     extra["defaultSnapshotVersion"] = "1.3-SNAPSHOT"
     val cacheRedirectorEnabled = findProperty("cacheRedirectorEnabled")?.toString()?.toBoolean() == true
 
-    kotlinBootstrapFrom(BootstrapOption.BintrayBootstrap("1.3.70-dev-1070", cacheRedirectorEnabled))
+    kotlinBootstrapFrom(BootstrapOption.BintrayBootstrap("1.3.70-dev-1140", cacheRedirectorEnabled))
 
     repositories {
         bootstrapKotlinRepo?.let(::maven)

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/tasks/Tasks.kt

@@ -567,6 +567,10 @@ open class Kotlin2JsCompile : AbstractKotlinCompile<K2JSCompilerArguments>(), Ko
             "-Xir-produce-klib-file"
         ).any(freeCompilerArgs::contains)
 
+    // Kotlin/JS can operate in 3 modes:
+    //  1) purely pre-IR backend
+    //  2) purely IR backend
+    //  3) hybrid pre-IR and IR backend. Can only accept libraries with both JS and IR parts.
     private val libraryFilter: (File) -> Boolean
         get() = if (kotlinOptions.isIrBackendEnabled()) {
             if (kotlinOptions.isPreIrBackendDisabled()) {