Do not reset freeCompilerArgs for some kotlin-native modules

Otherwise common compiler arguments which are set for all modules in the
project in `buildSrc/src/main/kotlin/common-configuration.gradle.kts`
are not applied. The most interesting of those are `-Xuse-k2` (if K2 is
enabled) and `-Xjvm-default=all`.

kotlin-native/Interop/Indexer/build.gradle.kts

@@ -176,7 +176,7 @@ val compileKotlin: org.jetbrains.kotlin.gradle.tasks.KotlinCompile by tasks
 tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>().configureEach {
     kotlinOptions {
         allWarningsAsErrors = true
-        freeCompilerArgs = listOf("-Xskip-prerelease-check")
+        freeCompilerArgs += listOf("-Xskip-prerelease-check")
     }
 }
 

kotlin-native/Interop/Runtime/build.gradle.kts

@@ -73,9 +73,8 @@ sourceSets.main.get().java.srcDir("src/jvm/kotlin")
 
 tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>().configureEach {
     kotlinOptions {
-        freeCompilerArgs = listOf(
+        freeCompilerArgs += listOf(
             "-opt-in=kotlin.ExperimentalUnsignedTypes",
-            "-opt-in=kotlin.RequiresOptIn",
             "-Xskip-prerelease-check"
         )
         allWarningsAsErrors = true

kotlin-native/Interop/StubGenerator/build.gradle.kts

@@ -46,9 +46,9 @@ dependencies {
 tasks {
     withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
         kotlinOptions {
-            freeCompilerArgs = listOf(
-                    "-opt-in=kotlin.ExperimentalUnsignedTypes",
-                    "-Xskip-metadata-version-check"
+            freeCompilerArgs += listOf(
+                "-opt-in=kotlin.ExperimentalUnsignedTypes",
+                "-Xskip-metadata-version-check"
             )
             allWarningsAsErrors = true
         }