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

native/utils/src/org/jetbrains/kotlin/konan/util/DefFile.kt

@@ -120,6 +120,10 @@ class DefFile(val file:File?, val config:DefFileConfig, val manifestAddendProper
             properties.getSpaceSeparated("exportForwardDeclarations")
         }
 
+        val allowedOverloadsForCFunctions by lazy {
+            properties.getSpaceSeparated("allowedOverloadsForCFunctions")
+        }
+
         val disableDesignatedInitializerChecks by lazy {
             properties.getProperty("disableDesignatedInitializerChecks")?.toBoolean() ?: false
         }