eg. test/lib/jdk/test/lib/util/JarUtils.java makes use of transferTo,
which is available since jdk9
(https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/InputStream.html#transferTo(java.io.OutputStream)

Another example is more tricky. the whitebox api isMethodCompilable doesn't work in test/lib/sun/hotspot/WhiteBox.java. It's because CompLevel_any=-1 in jdk8u. Whitebox APIs must be consistent with the implementation of hotspot.

I'd like to fix them because I'd like to use jdk/test/lib to run vmTestbase.
Otherwise, I have to check in another copy of same code in hotspot/test.