Swift export: add execution test for KT-66838

Author: mglukhikh

native/swift/swift-export-standalone-integration-tests/simple/testData/execution/vararg/vararg.kt

@@ -0,0 +1,13 @@
+// KIND: STANDALONE
+// FREE_COMPILER_ARGS: -opt-in=kotlin.native.internal.InternalForKotlinNative
+// MODULE: Vararg
+// FILE: Vararg.kt
+
+fun simple(a: String, vararg b: Int): String = buildString {
+    append(a)
+    b.forEach { append(it) }
+}
+
+class Accessor(vararg val x: Float) {
+    operator fun get(i: Int): Float = x[i]
+}

native/swift/swift-export-standalone-integration-tests/simple/testData/execution/vararg/vararg.swift

@@ -0,0 +1,13 @@
+import Vararg
+import KotlinRuntime
+import Testing
+
+@Test
+func testVararg() throws {
+    let x = simple(a: "a", b: 4, 5, 6)
+    try #require(x == "a456")
+
+    let accessor = Accessor(x: 3.14, 2.72)
+    try #require(accessor[0] > 3.1)
+    try #require(accessor[1] < 2.8)
+}