[K/JS] Throw error when a module contains file with the same name and package (ignoring case)

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/targets/js/ir/CompilerFlags.kt

@@ -24,6 +24,7 @@ internal const val MINIMIZED_MEMBER_NAMES = "-Xir-minimized-member-names"
 
 internal const val KLIB_MODULE_NAME = "-Xir-module-name"
 
+internal const val PER_FILE = "-Xir-per-file"
 internal const val PER_MODULE = "-Xir-per-module"
 internal const val PER_MODULE_OUTPUT_NAME = "-Xir-per-module-output-name"
 

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/targets/js/ir/OutputGranularity.kt

@@ -7,7 +7,8 @@ package org.jetbrains.kotlin.gradle.targets.js.ir
 
 enum class KotlinJsIrOutputGranularity {
     WHOLE_PROGRAM,
-    PER_MODULE;
+    PER_MODULE,
+    PER_FILE;
 
     companion object {
         fun byArgument(argument: String): KotlinJsIrOutputGranularity? =
@@ -17,6 +18,9 @@ enum class KotlinJsIrOutputGranularity {
 }
 
 fun KotlinJsIrOutputGranularity.toCompilerArgument(): String {
-    val perModule = this == KotlinJsIrOutputGranularity.PER_MODULE
-    return "$PER_MODULE=$perModule"
+    return when (this) {
+        KotlinJsIrOutputGranularity.PER_FILE -> PER_FILE
+        KotlinJsIrOutputGranularity.PER_MODULE -> PER_MODULE
+        KotlinJsIrOutputGranularity.WHOLE_PROGRAM -> ""
+    }
 }