Add CI environment variable properties for ARM

.ci/java-versions-aarch64.properties

@@ -0,0 +1,9 @@
+# This file is used with all of the non-matrix tests in Jenkins.
+
+# This .properties file defines the versions of Java with which to
+# build and test Elasticsearch for this branch. Valid Java versions
+# are 'java' or 'openjdk' followed by the major release number.
+
+ES_BUILD_JAVA=adoptopenjdk15
+ES_RUNTIME_JAVA=adoptopenjdk11
+GRADLE_TASK=build