build: add xx to cross-compile binaries in Docker

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

Dockerfile

@@ -1,19 +1,30 @@
 ARG BASE_IMAGE=alpine
 
-FROM golang:1.20.3-alpine3.16 AS builder
+FROM --platform=$BUILDPLATFORM tonistiigi/xx AS xx
+
+FROM --platform=$BUILDPLATFORM golang:1.20.3-alpine3.16 AS builder
+
+RUN apk add --no-cache --update alpine-sdk ca-certificates openssl clang lld
+
+COPY --from=xx / /
+
+ARG TARGETPLATFORM
+
+RUN CC=$(xx-info)-gcc
+RUN xx-go --wrap
+
+# gcc is only installed for libgcc
+RUN xx-apk --update --no-cache add musl-dev gcc
+
+# lld has issues building static binaries for ppc so prefer ld for it
+RUN [ "$(xx-info arch)" != "ppc64le" ] || XX_CC_PREFER_LINKER=ld xx-clang --setup-target-triple
 
 WORKDIR /usr/local/src/dex
 
-RUN apk add --no-cache --update alpine-sdk ca-certificates openssl
-
-ARG TARGETOS
-ARG TARGETARCH
-ARG TARGETVARIANT=""
-
-ENV GOOS=${TARGETOS} GOARCH=${TARGETARCH} GOARM=${TARGETVARIANT}
-
 ARG GOPROXY
 
+ENV CGO_ENABLED=1
+
 COPY go.mod go.sum ./
 COPY api/v2/go.mod api/v2/go.sum ./api/v2/
 RUN go mod download
@@ -37,8 +48,8 @@ ARG TARGETVARIANT
 ENV GOMPLATE_VERSION=v3.11.4
 
 RUN wget -O /usr/local/bin/gomplate \
-    "https://github.com/hairyhenderson/gomplate/releases/download/${GOMPLATE_VERSION}/gomplate_${TARGETOS:-linux}-${TARGETARCH:-amd64}${TARGETVARIANT}" \
-    && chmod +x /usr/local/bin/gomplate
+  "https://github.com/hairyhenderson/gomplate/releases/download/${GOMPLATE_VERSION}/gomplate_${TARGETOS:-linux}-${TARGETARCH:-amd64}${TARGETVARIANT}" \
+  && chmod +x /usr/local/bin/gomplate
 
 # For Dependabot to detect base image versions
 FROM alpine:3.17.3 AS alpine