Add iconv void * overloads for backwards compatibility

Since Xcode 15 the iconv APIs operate on an opaque type __tag_iconv_t* instead of
void*. This causes a runtime exception in older Ktor versions which
depended on iconv.

^KT-62286

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

@@ -431,7 +431,11 @@ class StubIrBuilder(private val context: StubIrContext) {
 
     private fun generateStubsForFunction(func: FunctionDecl) {
         try {
-            addStubs(FunctionStubBuilder(buildingContext, func, skipOverloads = true).build())
+            addStubs(FunctionStubBuilder(
+                    buildingContext,
+                    func,
+                    skipOverloads = func.name !in context.configuration.allowedOverloadsForCFunctions
+            ).build())
         } catch (e: Throwable) {
             context.log("Warning: cannot generate stubs for function ${func.name}")
         }

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

@@ -31,6 +31,7 @@ class InteropConfiguration(
         val nonStrictEnums: Set<String>,
         val noStringConversion: Set<String>,
         val exportForwardDeclarations: List<String>,
+        val allowedOverloadsForCFunctions: Set<String>,
         val disableDesignatedInitializerChecks: Boolean,
         val disableExperimentalAnnotation: Boolean,
         val target: KonanTarget

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

@@ -324,6 +324,7 @@ private fun processCLib(
             nonStrictEnums = def.config.nonStrictEnums.toSet(),
             noStringConversion = def.config.noStringConversion.toSet(),
             exportForwardDeclarations = def.config.exportForwardDeclarations,
+            allowedOverloadsForCFunctions = def.config.allowedOverloadsForCFunctions.toSet(),
             disableDesignatedInitializerChecks = def.config.disableDesignatedInitializerChecks,
             disableExperimentalAnnotation = cinteropArguments.disableExperimentalAnnotation ?: false,
             target = target