Refactor: improve Dockerfile (#2246)

Dockerfile

@@ -1,18 +1,22 @@
-FROM golang:alpine as builder
+FROM --platform=${BUILDPLATFORM} golang:alpine as builder
 
-RUN apk add --no-cache make git && \
+RUN apk add --no-cache make git ca-certificates tzdata && \
     wget -O /Country.mmdb https://github.com/Dreamacro/maxmind-geoip/releases/latest/download/Country.mmdb
-WORKDIR /clash-src
+WORKDIR /workdir
 COPY --from=tonistiigi/xx:golang / /
-COPY . /clash-src
-RUN go mod download && \
-    make docker && \
-    mv ./bin/clash-docker /clash
+ARG TARGETOS TARGETARCH TARGETVARIANT
+
+RUN --mount=target=. \
+    --mount=type=cache,target=/root/.cache/go-build \
+    --mount=type=cache,target=/go/pkg/mod \
+    make BINDIR= ${TARGETOS}-${TARGETARCH}${TARGETVARIANT} && \
+    mv /clash* /clash
 
 FROM alpine:latest
 LABEL org.opencontainers.image.source="https://github.com/Dreamacro/clash"
 
-RUN apk add --no-cache ca-certificates tzdata
+COPY --from=builder /usr/share/zoneinfo /usr/share/zoneinfo
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
 COPY --from=builder /Country.mmdb /root/.config/clash/
 COPY --from=builder /clash /
 ENTRYPOINT ["/clash"]

Makefile

@@ -37,9 +37,6 @@ WINDOWS_ARCH_LIST = \
 
 all: linux-amd64 darwin-amd64 windows-amd64 # Most used
 
-docker:
-	$(GOBUILD) -o $(BINDIR)/$(NAME)-$@
-
 darwin-amd64:
 	GOARCH=amd64 GOOS=darwin $(GOBUILD) -o $(BINDIR)/$(NAME)-$@