Zero: GTest tests fail with "unsuppported vm variant"

$ 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)