Dockerfile: cross compile images using native builder

Use a build image built for the native architecture so that it doesn't
run in emulation mode.

Switch to Chainguard's wolfi/glibc build image. This limits our build
architectures to just amd64 and arm64, but that is sufficient for our
needs.

Updates #42
Updates #43

Signed-off-by: Will Norris <[email protected]>

Dockerfile

@@ -1,12 +1,13 @@
-FROM cgr.dev/chainguard/go:1.19-musl as build
+FROM --platform=$BUILDPLATFORM cgr.dev/chainguard/go:1.19 as build
 
 WORKDIR /work
 
 COPY go.mod go.sum ./
 RUN go mod download
 
 COPY . .
-RUN CGO_ENABLED=0 GOOS=linux go build -v ./cmd/golink
+ARG TARGETOS TARGETARCH
+RUN CGO_ENABLED=0 GOOS=$TARGETOS GOARCH=$TARGETARCH go build -v ./cmd/golink
 
 
 FROM cgr.dev/chainguard/static:latest