[Gradle, JS] Rename flag for legacy

^KT-40320 fixed

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

@@ -205,8 +205,8 @@ internal class PropertiesProvider private constructor(private val project: Proje
     /**
      * Use Kotlin/JS backend compiler type
      */
-    val jsLegacyExecutableExplicitly: Boolean
-        get() = booleanProperty("kotlin.js.legacy.executable.explicitly") ?: false
+    val jsGenerateExecutableDefault: Boolean
+        get() = booleanProperty("kotlin.js.generate.executable.default") ?: true
 
     val stdlibDefaultDependency: Boolean
         get() = booleanProperty("kotlin.stdlib.default.dependency") ?: true

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

@@ -136,7 +136,7 @@ constructor(
         project.objects.newInstance(KotlinBrowserJs::class.java, this).also {
             it.configure()
 
-            if (!PropertiesProvider(project).jsLegacyExecutableExplicitly) {
+            if (PropertiesProvider(project).jsGenerateExecutableDefault) {
                 binaries.executable()
             }
 
@@ -163,7 +163,7 @@ constructor(
         project.objects.newInstance(KotlinNodeJs::class.java, this).also {
             it.configure()
 
-            if (!PropertiesProvider(project).jsLegacyExecutableExplicitly) {
+            if (PropertiesProvider(project).jsGenerateExecutableDefault) {
                 binaries.executable()
             }