RFR: 8256736: Zero: GTest tests fail with "unsupported vm variant"

[Aleksey Shipilev]

Manifests as `tier1` test:

$ CONF=linux-x86_64-zero-fastdebug make exploded-test TEST=jtreg:gtest/MetaspaceGtests.java

00:16:40 java.lang.Error: TESTBUG: unsuppported vm variant
00:16:40 at GTestWrapper.getJVMVariantSubDir(GTestWrapper.java:122)
00:16:40 at GTestWrapper.main(GTestWrapper.java:50)
00:16:40 at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
00:16:40 at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
00:16:40 at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
00:16:40 at java.base/java.lang.reflect.Method.invoke(Method.java:564)
00:16:40 at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:298)
00:16:40 at java.base/java.lang.Thread.run(Thread.java:831)

Let's make the wrapper know about the Zero variant.

Additional testing:
 - [x] Affected tests (they still fail, but because of Zero problems)

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

Commit messages:
 - 8256736: Zero: GTest tests fail with "unsupported vm variant"

Changes: https://git.openjdk.java.net/jdk/pull/1344/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1344&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256736
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1344.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1344/head:pull/1344

PR: https://git.openjdk.java.net/jdk/pull/1344