Switch test target to use XCTest to support testing older toolchains

Author: plemarquand

assets/test/targets/Tests/TargetsTests/TargetsTests.swift

@@ -1,4 +1,6 @@
-import Testing
+import XCTest
 
-@Test func example() async throws {
-}
+class TargetsTests: XCTestCase {
+    func testExample() {
+    }
+}