Minor, fix cpu arch compare to use correct Dockerfile (#6852)

start-build-env.sh

@@ -23,7 +23,7 @@ DOCKER_DIR=dev-support/docker
 DOCKER_FILE="${DOCKER_DIR}/Dockerfile"
 
 CPU_ARCH=$(echo "$MACHTYPE" | cut -d- -f1)
-if [[ "$CPU_ARCH" = "aarch64" || "$CPU_ARCH" = "arm64" ]]; then
+if [[ "$CPU_ARCH" == "aarch64" || "$CPU_ARCH" == "arm64" ]]; then
   DOCKER_FILE="${DOCKER_DIR}/Dockerfile_aarch64"
 fi