fix: Enhance Dockerfile for multi-platform support (#566)

Updated Dockerfile to support multi-platform builds and improved caching for Go dependencies.

Author: bakito

Dockerfile

@@ -1,17 +1,31 @@
-FROM golang:1.26-alpine AS builder
+# syntax=docker/dockerfile:1
+FROM --platform=$BUILDPLATFORM golang:1.26-alpine AS builder
 
 WORKDIR /build
 
-RUN apk update && apk add upx
+# Install build dependencies
+RUN apk update && apk add --no-cache upx git
 
 ARG VERSION=main
+ARG TARGETPLATFORM
+ARG BUILDPLATFORM
+ARG TARGETOS
+ARG TARGETARCH
+
 ENV GO111MODULE=on \
-    CGO_ENABLED=0 \
-    GOOS=linux
+    CGO_ENABLED=0
+
 COPY . .
 
-RUN go build -a -installsuffix cgo -ldflags="-w -s -X github.com/bakito/k8s-event-logger-operator/version.Version=${VERSION}" -o k8s-event-logger && \
-  upx -q k8s-event-logger
+RUN --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=cache,target=/root/.cache/go-build \
+    GOOS=${TARGETOS} GOARCH=${TARGETARCH} \
+    go build \
+      -a \
+      -installsuffix cgo \
+      -ldflags="-w -s -X github.com/bakito/k8s-event-logger-operator/version.Version=${VERSION}" \
+      -o k8s-event-logger . && \
+    upx -q k8s-event-logger
 
 # application image
 FROM scratch