[mkopecky@dhcp-10-40-4-197 71x] (master)$ grep  -Ri "ee8.preview"
testsuite/integration-tests/src/test/resources/arquillian.xml:                <property name="javaVmArguments">-server -Xms256m -Xmx1G -Djboss.bind.address=${node} -Djboss.bind.address.management=${node} -Dnode=${node} -Dipv6=${ipv6} ${additionalJvmArgs} ${modular.jdk.args} ${ipv6ArquillianSettings} ${jacoco.agent} -Dee8.preview.mode=${ee8.preview.mode} -Djboss.socket.binding.port-offset=${container.offset.manual.tracing} -Djboss.server.base.dir=${container.base.dir.manual.tracing}</property>
[mkopecky@dhcp-10-40-4-197 71x] (master)$ 

[mkopecky@dhcp-10-40-4-197 71x2] (3.6)$ grep  -Ri "ee8.preview"
testsuite/pom.xml:        <ee8.preview.mode>true</ee8.preview.mode>
[mkopecky@dhcp-10-40-4-197 71x2] (3.6)$