Fix multiplatform build Dockerfile

Author: anhthii

Dockerfile

@@ -1,7 +1,7 @@
 FROM golang:1.25 AS builder
 
-ARG TARGETOS=linux
-ARG TARGETARCH=amd64
+ARG TARGETOS
+ARG TARGETARCH
 
 WORKDIR /src
 
@@ -13,7 +13,9 @@ COPY . .
 
 RUN --mount=type=cache,target=/go/pkg/mod \
     --mount=type=cache,target=/root/.cache/go-build \
-    CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} \
+    CGO_ENABLED=0 \
+    GOOS=${TARGETOS} \
+    GOARCH=${TARGETARCH} \
     go build -o /out/mpcium ./cmd/mpcium
 
 FROM gcr.io/distroless/base-debian12:latest