fix: docker file legacy expression

docker/Dockerfile

@@ -4,16 +4,16 @@ SHELL ["/bin/sh", "-x", "-c"]
 ENV SERIAL 2
 
 ########################################
-FROM base as builder
+FROM base AS builder
 
-ENV CFLAGS=-Ofast
-ENV BUILD_DEPS curl make ca-certificates build-essential pkg-config libssl-dev libclang-dev cmake
+ARG CFLAGS=-Ofast
+ARG BUILD_DEPS="curl make ca-certificates build-essential pkg-config libssl-dev libclang-dev cmake"
 
 WORKDIR /tmp
 
 COPY . /tmp/
 
-ENV RUSTFLAGS "-C link-arg=-s"
+ARG RUSTFLAGS="-C link-arg=-s"
 
 RUN update-ca-certificates 2> /dev/null || true
 
@@ -29,7 +29,7 @@ RUN apt-get update && apt-get install -qy --no-install-recommends $BUILD_DEPS &&
 FROM base AS runner
 LABEL maintainer="Jun Kurihara"
 
-ENV RUNTIME_DEPS logrotate ca-certificates gosu
+ARG RUNTIME_DEPS="logrotate ca-certificates gosu"
 
 RUN apt-get update && \
     apt-get install -qy --no-install-recommends $RUNTIME_DEPS && \