Fix build

ap-relay/Dockerfile.arm64v8

@@ -5,26 +5,26 @@ ARG TAG
 ARG GIT_REPOSITORY
 ARG BUILD_DATE
 
-ARG UID=991
-ARG GID=991
-
 RUN git clone -b ${TAG} ${GIT_REPOSITORY} /opt/relay
 WORKDIR /opt/relay
 RUN cargo install --path .
 
 FROM arm64v8/ubuntu:19.10
 
+ARG UID=991
+ARG GID=991
+
 RUN \
  apt-get update && \
  apt-get upgrade -y
 
 RUN \
- addgroup --gid "$GID" relay && \
+ addgroup --gid "${GID}" relay && \
  adduser \
     --disabled-password \
     --gecos "" \
     --ingroup relay \
-    --uid "$UID" \
+    --uid "${UID}" \
     relay
 
 COPY --from=builder /usr/local/cargo/bin/ap-actix /usr/local/bin/relay