Use native docker images for scripts on aarch64 Host OS

Commit 051b05b7 support aach64 Host OS to execute scripts. However, it
does not set DOCKER_BASE parameter which consequently uses x86_64 docker
images instead of arm64v8 image.
This commit sets DOCKER_BASE to arm64v8/ to use native docker images.

Tested:
1. Set environment variables appropriately and execute scripts. Ensure
all docker images loaded successfully and scripts can execute without
issue.

Signed-off-by: Thang Q. Nguyen <thang@os.amperecomputing.com>
Change-Id: I3c09d448dae17f290f2c2fd1d8116167510635b6
diff --git a/build-jenkins.sh b/build-jenkins.sh
index 2ef4129..cdc61cb 100755
--- a/build-jenkins.sh
+++ b/build-jenkins.sh
@@ -114,7 +114,7 @@
     tini_arch="amd64"
     ;;
   "aarch64")
-    docker_base=""
+    docker_base="arm64v8/"
     tini_arch="arm64"
     ;;
   *)
diff --git a/build-rootfs-size-docker.sh b/build-rootfs-size-docker.sh
index cde66e6..36876f4 100755
--- a/build-rootfs-size-docker.sh
+++ b/build-rootfs-size-docker.sh
@@ -22,7 +22,7 @@
         DOCKER_BASE=""
         ;;
     "aarch64")
-        DOCKER_BASE=""
+        DOCKER_BASE="arm64v8/"
         ;;
     *)
         echo "Unsupported system architecture(${ARCH}) found for docker image"
diff --git a/build-setup.sh b/build-setup.sh
index 9750b5f..3fd9fc1 100755
--- a/build-setup.sh
+++ b/build-setup.sh
@@ -124,7 +124,7 @@
     DOCKER_BASE=""
     ;;
   "aarch64")
-    DOCKER_BASE=""
+    DOCKER_BASE="arm64v8/"
     ;;
   *)
     echo "Unsupported system architecture(${ARCH}) found for docker image"
diff --git a/openpower-build-setup.sh b/openpower-build-setup.sh
index 1ca5f25..3d8bc73 100755
--- a/openpower-build-setup.sh
+++ b/openpower-build-setup.sh
@@ -36,7 +36,7 @@
         DOCKER_BASE=""
         ;;
     "aarch64")
-        DOCKER_BASE=""
+        DOCKER_BASE="arm64v8/"
         ;;
     *)
         echo "Unsupported system architecture(${ARCH}) found for docker image"
diff --git a/qemu-build.sh b/qemu-build.sh
index 6005128..6a60abd 100755
--- a/qemu-build.sh
+++ b/qemu-build.sh
@@ -57,7 +57,7 @@
     DOCKER_BASE=""
     ;;
   "aarch64")
-    DOCKER_BASE=""
+    DOCKER_BASE="arm64v8/"
     ;;
   *)
     echo "Unsupported system architecture(${ARCH}) found for docker image"
diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index 3de35cc..a22843d 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -690,7 +690,7 @@
 elif arch == "x86_64":
     docker_base = ""
 elif arch == "aarch64":
-    docker_base = ""
+    docker_base = "arm64v8/"
 else:
     print(
         f"Unsupported system architecture({arch}) found for docker image",