[Test] Introduce appropriate runtime availability check

Author: DougGregor

test/stdlib/ErrorBridged.swift

@@ -776,20 +776,22 @@ func anyToAny<T, U>(_ a: T, _ : U.Type) -> U {
 ErrorBridgingTests.test("error-to-NSObject casts") {
   let error = MyCustomizedError(code: 12345)
 
-  // Unconditional cast
-  let nsErrorAsObject1 = unconditionalCast(error, to: NSObject.self)
-  let nsError1 = unconditionalCast(nsErrorAsObject1, to: NSError.self)
-  expectEqual("custom", nsError1.domain)
-  expectEqual(12345, nsError1.code)
-
-  // Conditional cast
-  let nsErrorAsObject2 = conditionalCast(error, to: NSObject.self)!
-  let nsError2 = unconditionalCast(nsErrorAsObject2, to: NSError.self)
-  expectEqual("custom", nsError2.domain)
-  expectEqual(12345, nsError2.code)
-
-  // "is" check
-  expectTrue(error is NSObject)
+  if #available(macOS 9999, iOS 9999, tvOS 9999, watchOS 9999, *) {
+    // Unconditional cast
+    let nsErrorAsObject1 = unconditionalCast(error, to: NSObject.self)
+    let nsError1 = unconditionalCast(nsErrorAsObject1, to: NSError.self)
+    expectEqual("custom", nsError1.domain)
+    expectEqual(12345, nsError1.code)
+
+    // Conditional cast
+    let nsErrorAsObject2 = conditionalCast(error, to: NSObject.self)!
+    let nsError2 = unconditionalCast(nsErrorAsObject2, to: NSError.self)
+    expectEqual("custom", nsError2.domain)
+    expectEqual(12345, nsError2.code)
+
+    // "is" check
+    expectTrue(error is NSObject)
+  }
 }
 
 runAllTests()