Adopt configuration-avoidance where possible

Before this change `./gradlew help` (with native enabled)
Created immediately: 1322
Created during configuration: 1541

after this change:
Created immediately: 596
Created during configuration: 1509

To know more about configuration avoidance: https://docs.gradle.org/current/userguide/task_configuration_avoidance.html

kotlin-native/runtime/build.gradle.kts

@@ -406,7 +406,7 @@ val hostRuntimeTests by tasks.registering {
     dependsOn("${hostName}RuntimeTests")
 }
 
-val assemble by tasks.getting {
+tasks.named("assemble") {
     dependsOn(targetList.map { "${it}Runtime" })
 }
 
@@ -414,7 +414,7 @@ val hostAssemble by tasks.registering {
     dependsOn("${hostName}Runtime")
 }
 
-val clean by tasks.getting {
+tasks.named("clean") {
     doFirst {
         delete(buildDir)
     }