Update packer cache script to be compatibile with aarch64 workers

.ci/packer_cache.sh

@@ -15,21 +15,28 @@ while [ -h "$SCRIPT" ] ; do
   fi
 done
 
-source $(dirname "${SCRIPT}")/java-versions.properties
-## We are caching BWC versions too, need these so we can build those
-export JAVA8_HOME="${HOME}"/.java/java8
-export JAVA11_HOME="${HOME}"/.java/java11
-export JAVA12_HOME="${HOME}"/.java/openjdk12
-export JAVA13_HOME="${HOME}"/.java/openjdk13
-export JAVA14_HOME="${HOME}"/.java/openjdk14
+if [ "$(uname -m)" = "arm64" ] || [ "$(uname -m)" = "aarch64" ]; then
+  ## On ARM we use a different properties file for setting java home
+  ## Also, we don't bother attempting to resolve dependencies for the 6.8 branch
+  source $(dirname "${SCRIPT}")/java-versions-aarch64.properties
+else
+  source $(dirname "${SCRIPT}")/java-versions.properties
+  ## We are caching BWC versions too, need these so we can build those
+  export JAVA8_HOME="${HOME}"/.java/java8
+  export JAVA11_HOME="${HOME}"/.java/java11
+  export JAVA12_HOME="${HOME}"/.java/openjdk12
+  export JAVA13_HOME="${HOME}"/.java/openjdk13
+  export JAVA14_HOME="${HOME}"/.java/openjdk14
+
+  ## 6.8 branch is not referenced from any bwc project in master so we need to
+  ## resolve its dependencies explicitly
+  rm -rf checkout/6.8
+  git clone --reference $(dirname "${SCRIPT}")/../.git https://github.com/elastic/elasticsearch.git --branch 6.8 --single-branch checkout/6.8
+  export JAVA_HOME="${JAVA11_HOME}"
+  ./checkout/6.8/gradlew --project-dir ./checkout/6.8 --parallel clean --scan -Porg.elasticsearch.acceptScanTOS=true --stacktrace resolveAllDependencies
+  rm -rf ./checkout/6.8
+fi
 
-## 6.8 branch is not referenced from any bwc project in master so we need to
-## resolve its dependencies explicitly
-rm -rf checkout/6.8
-git clone --reference $(dirname "${SCRIPT}")/../.git https://github.com/elastic/elasticsearch.git --branch 6.8 --single-branch checkout/6.8
-export JAVA_HOME="${JAVA11_HOME}"
-./checkout/6.8/gradlew --project-dir ./checkout/6.8 --parallel clean --scan -Porg.elasticsearch.acceptScanTOS=true --stacktrace resolveAllDependencies
-rm -rf ./checkout/6.8
 ## Gradle is able to resolve dependencies resolved with earlier gradle versions
 ## therefore we run master _AFTER_ we run 6.8 which uses an earlier gradle version
 export JAVA_HOME="${HOME}"/.java/${ES_BUILD_JAVA}