Disable SigV4a tests on Native

Author: lauzadis

runtime/auth/aws-signing-default/common/test/aws/smithy/kotlin/runtime/auth/awssigning/SigV4aSignatureCalculatorTest.kt

@@ -4,6 +4,7 @@
  */
 package aws.smithy.kotlin.runtime.auth.awssigning
 
+import aws.smithy.kotlin.runtime.IgnoreNative
 import aws.smithy.kotlin.runtime.auth.awscredentials.Credentials
 import aws.smithy.kotlin.runtime.time.Instant
 import aws.smithy.kotlin.runtime.util.PlatformProvider
@@ -68,6 +69,7 @@ private val TESTS = listOf(
  * Tests for [SigV4aSignatureCalculator]. Currently only tests forming the string-to-sign.
  */
 class SigV4aSignatureCalculatorTest {
+    @IgnoreNative // FIXME test resources are not loadable on iOS: https://youtrack.jetbrains.com/issue/KT-49981/
     @Test
     fun testStringToSign() = TESTS.forEach { testId ->
         runTest {