Maintenance: better layer caching

- Install g++ in base image before copying code
- Install xcputranslate in base image before copying code
- Install golangci-lint in base image before copying code
- Install golangci-lint using go get directly

Dockerfile

@@ -3,8 +3,11 @@ ARG GO_VERSION=1.16
 ARG BUILDPLATFORM=linux/amd64
 
 FROM --platform=$BUILDPLATFORM golang:${GO_VERSION}-alpine${ALPINE_VERSION} AS base
-RUN apk --update add git
+RUN apk --update add git g++
 ENV CGO_ENABLED=0
+COPY --from=qmcgaw/xcputranslate:v0.4.0 /xcputranslate /usr/local/bin/xcputranslate
+ARG GOLANGCI_LINT_VERSION=v1.40.1
+RUN go get github.com/golangci/golangci-lint/cmd/golangci-lint@${GOLANGCI_LINT_VERSION}
 WORKDIR /tmp/gobuild
 COPY go.mod go.sum ./
 RUN go mod download
@@ -14,15 +17,11 @@ COPY internal/ ./internal/
 FROM --platform=$BUILDPLATFORM base AS test
 # Note on the go race detector:
 # - we set CGO_ENABLED=1 to have it enabled
-# - we install g++ to support the race detector
+# - we installed g++ to support the race detector
 ENV CGO_ENABLED=1
-RUN apk --update --no-cache add g++
 ENTRYPOINT go test -race -coverpkg=./... -coverprofile=coverage.txt -covermode=atomic ./...
 
 FROM --platform=$BUILDPLATFORM base AS lint
-ARG GOLANGCI_LINT_VERSION=v1.40.1
-RUN wget -O- -nv https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | \
-    sh -s -- -b /usr/local/bin ${GOLANGCI_LINT_VERSION}
 COPY .golangci.yml ./
 RUN golangci-lint run --timeout=10m
 
@@ -36,7 +35,6 @@ RUN git init && \
     git diff --exit-code -- go.mod
 
 FROM --platform=$BUILDPLATFORM base AS build
-COPY --from=qmcgaw/xcputranslate:v0.4.0 /xcputranslate /usr/local/bin/xcputranslate
 ARG TARGETPLATFORM
 ARG VERSION=unknown
 ARG BUILD_DATE="an unknown date"