Detect Docker image platform automatically

cloudbuild.yaml

@@ -8,7 +8,7 @@ steps:
       docker build \
         -t darthsim/imgproxy:$TAG_NAME-amd64 \
         -f docker/Dockerfile \
-        --build-arg TARGET_ARCH="amd64" \
+        --platform=linux/amd64 \
         .
   env:
     - DOCKER_BUILDKIT=1
@@ -24,8 +24,7 @@ steps:
       && docker build \
         -t darthsim/imgproxy:$TAG_NAME-arm64 \
         -f docker/Dockerfile \
-        --platform=arm64 \
-        --build-arg TARGET_ARCH="arm64" \
+        --platform=linux/arm64/v8 \
         .
   env:
     - DOCKER_BUILDKIT=1

docker/Dockerfile

@@ -1,7 +1,6 @@
 ARG BASE_IMAGE_VERSION="v3.1.0"
-ARG TARGET_ARCH="amd64"
 
-FROM --platform=${TARGET_ARCH} darthsim/imgproxy-base:${BASE_IMAGE_VERSION}
+FROM darthsim/imgproxy-base:${BASE_IMAGE_VERSION}
 
 COPY . .
 RUN ["bash", "-c", "go build -v -o /usr/local/bin/imgproxy"]
@@ -9,7 +8,7 @@ RUN ["bash", "-c", "go build -v -o /usr/local/bin/imgproxy"]
 # ==================================================================================================
 # Final image
 
-FROM --platform=${TARGET_ARCH} debian:bullseye-slim
+FROM debian:bullseye-slim
 LABEL maintainer="Sergey Alexandrovich <darthsim@gmail.com>"
 
 RUN apt-get update \