RFR: 8255915: jdk/incubator/vector/AddTest.java timed out

[Paul Sandoz]

Update the test to require C2, since under execution with -Xcomp and C1 only this test can time out.

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Commit messages:
 - Require C2 for test execution

Changes: https://git.openjdk.java.net/jdk/pull/3718/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3718&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255915
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3718.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3718/head:pull/3718

PR: https://git.openjdk.java.net/jdk/pull/3718