add kokoro job configs for php aarch64 linux test

kokoro/linux/php_aarch64/build.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+#
+# This is the top-level script we give to Kokoro as the entry point for
+# running the "continuous" and "presubmit" jobs.
+
+set -ex
+
+# Change to repo root
+cd $(dirname $0)/../../..
+
+# Initialize any submodules.
+git submodule update --init --recursive
+
+kokoro/linux/aarch64/qemu_helpers/prepare_qemu.sh
+
+kokoro/linux/aarch64/test_php_aarch64.sh

kokoro/linux/php_aarch64/continuous.cfg

@@ -0,0 +1,11 @@
+# Config file for running tests in Kokoro
+
+# Location of the build script in repository
+build_file: "protobuf/kokoro/linux/php_aarch64/build.sh"
+timeout_mins: 120
+
+action {
+  define_artifacts {
+    regex: "**/sponge_log.xml"
+  }
+}

kokoro/linux/php_aarch64/presubmit.cfg

@@ -0,0 +1,11 @@
+# Config file for running tests in Kokoro
+
+# Location of the build script in repository
+build_file: "protobuf/kokoro/linux/php_aarch64/build.sh"
+timeout_mins: 120
+
+action {
+  define_artifacts {
+    regex: "**/sponge_log.xml"
+  }
+}