[jdk21u-dev] RFR: 8319571: Update jni/nullCaller/NullCallerTest.java to accept flags or mark as flagless

[Goetz Lindenmaier]

I backport this for parity with 21.0.4-oracle.

-------------

Commit messages:
 - Backport b78896b9aafcb15f453eaed6e154a5461581407b

Changes: https://git.openjdk.org/jdk21u-dev/pull/399/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=399&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319571
  Stats: 27 lines in 1 file changed: 1 ins; 21 del; 5 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/399.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/399/head:pull/399

PR: https://git.openjdk.org/jdk21u-dev/pull/399