[Build] Fix a bunch of buildscript compilation warnings

#KTI-1221 Fixed

libraries/stdlib/js-ir-minimal-for-test/build.gradle.kts

@@ -125,11 +125,11 @@ val jsMainSources by task<Sync> {
 
 kotlin {
     sourceSets {
-        val commonMain by getting {
+        named("commonMain") {
             kotlin.srcDir(files(commonMainSources.map { it.destinationDir }))
             kotlin.srcDir(files(commonMainCollectionSources.map { it.destinationDir }))
         }
-        val jsMain by getting {
+        named("jsMain") {
             kotlin.srcDir(files(jsMainSources.map { it.destinationDir }))
         }
     }

libraries/stdlib/js-ir/build.gradle.kts

@@ -113,22 +113,22 @@ val jsTestSources by task<Sync> {
 
 kotlin {
     sourceSets {
-        val commonMain by getting {
+        named("commonMain") {
             kotlin.srcDir(files(commonMainSources.map { it.destinationDir }))
         }
-        val jsMain by getting {
+        named("jsMain") {
             kotlin.srcDir(files(jsMainSources.map { it.destinationDir }))
             kotlin.srcDir("builtins")
             kotlin.srcDir("runtime")
             kotlin.srcDir("src")
         }
-        val commonTest by getting {
+        named("commonTest") {
             dependencies {
                 api(project(":kotlin-test:kotlin-test-js-ir"))
             }
             kotlin.srcDir(files(commonTestSources.map { it.destinationDir }))
         }
-        val jsTest by getting {
+        named("jsTest") {
             dependencies {
                 api(project(":kotlin-test:kotlin-test-js-ir"))
             }

libraries/stdlib/wasm/build.gradle.kts

@@ -78,29 +78,30 @@ val commonTestSources by task<Sync> {
 D8RootPlugin.apply(rootProject).version = v8Version
 
 kotlin {
+    @OptIn(org.jetbrains.kotlin.gradle.targets.js.dsl.ExperimentalWasmDsl::class)
     wasm {
         d8()
     }
 
     sourceSets {
-        val wasmMain by getting {
+        named("wasmMain") {
             kotlin.srcDirs("builtins", "internal", "runtime", "src", "stubs")
             kotlin.srcDirs("$rootDir/libraries/stdlib/native-wasm/src")
             kotlin.srcDirs(files(builtInsSources.map { it.destinationDir }))
         }
 
-        val commonMain by getting {
+        named("commonMain") {
             kotlin.srcDirs(files(commonMainSources.map { it.destinationDir }))
         }
 
-        val commonTest by getting {
+        named("commonTest") {
             dependencies {
                 api(project(":kotlin-test:kotlin-test-wasm"))
             }
             kotlin.srcDir(files(commonTestSources.map { it.destinationDir }))
         }
 
-        val wasmTest by getting {
+        named("wasmTest") {
             dependencies {
                 api(project(":kotlin-test:kotlin-test-wasm"))
             }