Support variadic Objective-C methods

backend.native/tests/interop/objc/smoke.kt

@@ -21,6 +21,7 @@ fun run() {
     testExceptions()
     testBlocks()
     testCustomRetain()
+    testVarargs()
 
     assertEquals(2, ForwardDeclaredEnum.TWO.value)
 
@@ -256,6 +257,32 @@ fun testCustomRetain() {
     assertFalse(unexpectedDeallocation)
 }
 
+fun testVarargs() {
+    assertEquals(
+            "a b -1",
+            TestVarargs.testVarargsWithFormat(
+                    "%@ %s %d",
+                    "a" as NSString, "b".cstr, (-1).toByte()
+            ).formatted
+    )
+
+    assertEquals(
+            "2 3 9223372036854775807",
+            TestVarargs(
+                    "%d %d %lld",
+                    2.toShort(), 3, Long.MAX_VALUE
+            ).formatted
+    )
+
+    assertEquals(
+            "0.1 0.2 1 0",
+            TestVarargs.create(
+                    "%.1f %.1lf %d %d",
+                    0.1.toFloat(), 0.2, true, false
+            ).formatted
+    )
+}
+
 private class MyException : Throwable()
 
 fun nsArrayOf(vararg elements: Any): NSArray = NSMutableArray().apply {