[JIT] Mark AI-Extension unit test as flagless

Summary: AI-Extension runs tests by launching separate JVM processes. It does not rely on compilation flags added in `jtreg`, so this test should be marked as `flagless`.

Testing: test/hotspot/jtreg/compiler/alibaba/TestAIExtension.java

Reviewers: kuaiwei, JoshuaZhuwj

Issue: #977

Author: MaxXSoft

test/hotspot/jtreg/compiler/alibaba/TestAIExtension.java

@@ -24,7 +24,7 @@
 /**
  * @test TestAIExtension
  * @summary Check that the AI-Extension feature works correctly
- * @requires vm.aiext
+ * @requires vm.aiext & vm.flagless
  * @library /test/lib /
  * @build sun.hotspot.WhiteBox
  * @run driver ClassFileInstaller sun.hotspot.WhiteBox