Native: workaround KT-59552 in filecheck_single_tls_load test

After recent changes (0cfb801) println got inlined into the checked
function. As a result, the test became affected by KT-59552.

Fix the test by moving println out of the checked function.

kotlin-native/backend.native/tests/filecheck/single_tls_load.kt

@@ -5,16 +5,18 @@
 
 class Wrapper(x: Int)
 
-// CHECK-LABEL: "kfun:#f(kotlin.Int;kotlin.String){}"
-fun f(x: Int, s: String) {
+// CHECK-LABEL: "kfun:#f(kotlin.Int;kotlin.String){}kotlin.String"
+fun f(x: Int, s: String): String {
     // CHECK: _ZN6kotlin2mm14ThreadRegistry22currentThreadDataNode_E
     // CHECK-NOT: _ZN6kotlin2mm14ThreadRegistry22currentThreadDataNode_E
     if (x < 0) throw IllegalStateException()
     if (x > 0) return f(x - 1, s)
     val b = Wrapper(2)
     val a = listOf(x, x, Wrapper(1), 2, x)
-    for (i in a) { println("$s i") }
+    return buildString {
+        for (i in a) { appendLine("$s i") }
+    }
 // CHECK: {{^}$}}
 }
 
-fun main() { f(10, "123456") }
+fun main() { println(f(10, "123456")) }