[JS IR BE] Migrate JS BE to common klib utils

compiler/util-klib/src/org/jetbrains/kotlin/library/impl/KotlinLibraryLayoutImpl.kt

@@ -139,7 +139,7 @@ internal fun zippedKotlinLibraryChecks(klibFile: File) {
     check(klibFile.isFile) { "Expected $klibFile to be a regular file." }
 
     val extension = klibFile.extension
-    check(extension.isEmpty() || extension == KLIB_FILE_EXTENSION) {
+    check(extension.isEmpty() || extension == KLIB_FILE_EXTENSION || extension == "jar") {
         "KLIB path has unexpected extension: $klibFile"
     }
 }

compiler/util-klib/src/org/jetbrains/kotlin/library/impl/KotlinLibraryWriterImpl.kt

@@ -85,7 +85,7 @@ class KoltinLibraryWriterImpl(
 
 ) : BaseWriter by base, MetadataWriter by metadata, IrWriter by ir, KotlinLibraryWriter
 
-internal fun buildKoltinLibrary(
+fun buildKoltinLibrary(
     linkDependencies: List<KotlinLibrary>,
     metadata: SerializedMetadata,
     ir: SerializedIr,