Support 'exportForwardDeclarations' internal .def file option

Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/InteropConfiguration.kt

@@ -27,5 +27,6 @@ class InteropConfiguration(
         val excludedFunctions: Set<String>,
         val strictEnums: Set<String>,
         val nonStrictEnums: Set<String>,
-        val noStringConversion: Set<String>
+        val noStringConversion: Set<String>,
+        val exportForwardDeclarations: List<String>
 )

Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/StubGenerator.kt

@@ -995,12 +995,16 @@ class StubGenerator(
     }
 
     fun addManifestProperties(properties: Properties) {
-        properties["exportForwardDeclarations"] = nativeIndex.structs
+        val exportForwardDeclarations = configuration.exportForwardDeclarations.toMutableList()
+
+        nativeIndex.structs
                 .filter { it.def == null }
-                .joinToString(" ") {
+                .mapTo(exportForwardDeclarations) {
                     "$cnamesStructsPackageName.${it.kotlinName}"
                 }
 
+        properties["exportForwardDeclarations"] = exportForwardDeclarations.joinToString(" ")
+
         // TODO: consider exporting Objective-C class and protocol forward refs.
     }
 

Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt

@@ -275,7 +275,8 @@ private fun processCLib(args: Array<String>): Array<String>? {
             excludedFunctions = excludedFunctions,
             strictEnums = def.config.strictEnums.toSet(),
             nonStrictEnums = def.config.nonStrictEnums.toSet(),
-            noStringConversion = def.config.noStringConversion.toSet()
+            noStringConversion = def.config.noStringConversion.toSet(),
+            exportForwardDeclarations = def.config.exportForwardDeclarations
     )
 
     val nativeIndex = buildNativeIndex(library)

shared/src/main/kotlin/org/jetbrains/kotlin/konan/util/DefFile.kt

@@ -95,6 +95,10 @@ class DefFile(val file:File?, val config:DefFileConfig, val manifestAddendProper
         val depends by lazy {
             properties.getSpaceSeparated("depends")
         }
+
+        val exportForwardDeclarations by lazy {
+            properties.getSpaceSeparated("exportForwardDeclarations")
+        }
     }
 }