Allow libraries to have empty ir/ component.

shared/src/library/kotlin/org/jetbrains/kotlin/konan/library/KonanLibrary.kt

@@ -43,7 +43,7 @@ interface KonanLibrary {
     fun packageMetadataParts(fqName: String): Set<String>
     fun packageMetadata(fqName: String, partName: String): ByteArray
 
-    val irHeader: ByteArray
+    val irHeader: ByteArray?
     fun irDeclaration(index: Long, isLocal: Boolean): ByteArray
 }
 

shared/src/library/kotlin/org/jetbrains/kotlin/konan/library/KonanLibraryLayout.kt

@@ -50,7 +50,7 @@ interface KonanLibraryLayout {
         = File(irDir, "hidden_$declarationId.knd")
     fun visibleDeclarationFile(declarationId: String)
         = File(irDir, "visible_$declarationId.knd")
-    val wholeIrFile
+    val irHeader
         get() = File(irDir, "irHeaders.kni")
     val irIndex: File
         get() = File(irDir, "uniqIdTableDump.txt")

shared/src/library/kotlin/org/jetbrains/kotlin/konan/library/KonanMetadataReader.kt

@@ -3,6 +3,6 @@ package org.jetbrains.kotlin.konan.library
 interface MetadataReader {
     fun loadSerializedModule(libraryLayout: KonanLibraryLayout): ByteArray
     fun loadSerializedPackageFragment(libraryLayout: KonanLibraryLayout, fqName: String, partName: String): ByteArray
-    fun loadWholeIr(libraryLayout: KonanLibraryLayout): ByteArray
+    fun loadIrHeader(libraryLayout: KonanLibraryLayout): ByteArray
     fun loadIrDeclaraton(libraryLayout: KonanLibraryLayout, index: Long, isLocal: Boolean): ByteArray
 }

shared/src/library/kotlin/org/jetbrains/kotlin/konan/library/impl/DefaultMetadataReaderImpl.kt

@@ -11,8 +11,8 @@ internal object DefaultMetadataReaderImpl : MetadataReader {
     override fun loadSerializedPackageFragment(libraryLayout: KonanLibraryLayout, fqName: String, partName: String): ByteArray =
             libraryLayout.packageFragmentFile(fqName, partName).readBytes()
 
-    override fun loadWholeIr(libraryLayout: KonanLibraryLayout): ByteArray =
-            libraryLayout.wholeIrFile.readBytes()
+    override fun loadIrHeader(libraryLayout: KonanLibraryLayout): ByteArray =
+            libraryLayout.irHeader.readBytes()
 
     override fun loadIrDeclaraton(libraryLayout: KonanLibraryLayout, index: Long, isLocal: Boolean): ByteArray {
         val name = index.toULong().toString(16)

shared/src/library/kotlin/org/jetbrains/kotlin/konan/library/impl/KonanLibraryImpl.kt

@@ -84,7 +84,7 @@ class KonanLibraryImpl(
                 }
             }
 
-    override val irHeader: ByteArray by lazy { layout.inPlace {  metadataReader.loadWholeIr(it) }}
+    override val irHeader: ByteArray? by lazy { layout.inPlace { library -> library.irHeader.let { if (it.exists) metadataReader.loadIrHeader(library) else null }}}
 
     override fun irDeclaration(index: Long, isLocal: Boolean) = layout.inPlace { metadataReader.loadIrDeclaraton(it, index, isLocal) }