Simplify build script in Docker

docker/Dockerfile

@@ -2,8 +2,8 @@ ARG BASE_IMAGE_VERSION="v3.9.0"
 
 FROM darthsim/imgproxy-base:${BASE_IMAGE_VERSION}
 
-ARG BUILDPLATFORM
-ARG TARGETPLATFORM
+ARG TARGETARCH
+ARG BUILDARCH
 
 COPY . .
 RUN docker/build.sh

docker/build.sh

@@ -3,50 +3,21 @@
 set -e
 
 # This is pretty dirty hack. Building imgproxy under Qemu is pretty slow.
-# So we install Go binary native for the BUILDPLATFORM.
-if [[ $BUILDPLATFORM != $TARGETPLATFORM ]]; then
-  case "$BUILDPLATFORM" in
-    amd64 | "linux/amd64")
-      BUILD_ARCH="amd64"
-      ;;
-
-    arm64 | "arm64/v8" | "linux/arm64" | "linux/arm64/v8")
-      BUILD_ARCH="arm64"
-      ;;
-
-    *)
-      echo "Unknown platform: $BUILDPLATFORM"
-      exit 1
-  esac
-
-  case "$TARGETPLATFORM" in
-    amd64 | "linux/amd64")
-      TARGET_ARCH="amd64"
-      ;;
-
-    arm64 | "arm64/v8" | "linux/arm64" | "linux/arm64/v8")
-      TARGET_ARCH="arm64"
-      ;;
-
-    *)
-      echo "Unknown platform: $TARGETPLATFORM"
-      exit 1
-  esac
-
+# So we install Go binary native for the BUILDARCH.
+if [[ $BUILDARCH != $TARGETARCH ]]; then
   GOLANG_VERSION=$(go version | sed -E 's/.*go([0-9]+\.[0-9]+(\.[0-9]+)?).*/\1/')
 
   rm -rf /usr/local/go
 
-  dpkg --add-architecture ${BUILD_ARCH}
   apt-get update
-  apt-get install -y --no-install-recommends libstdc++6:${BUILD_ARCH}
+  apt-get install -y --no-install-recommends libstdc++6:${BUILDARCH}
 
-  curl -Ls https://golang.org/dl/go${GOLANG_VERSION}.linux-${BUILD_ARCH}.tar.gz \
+  curl -Ls https://golang.org/dl/go${GOLANG_VERSION}.linux-${BUILDARCH}.tar.gz \
     | tar -xzC /usr/local
 
   export CGO_ENABLED=1
   export GOOS=linux
-  export GOARCH=$TARGET_ARCH
+  export GOARCH=$TARGETARCH
 fi
 
 go build -v -ldflags "-s -w" -o /usr/local/bin/imgproxy