create multi-platform dockerfile

Author: osterman

Diff for: Dockerfile

@@ -1,12 +1,39 @@
-FROM debian:bookworm-slim
+FROM --platform=$BUILDPLATFORM debian:bookworm-slim
+
+ARG TARGETPLATFORM
+ARG BUILDPLATFORM
+
+# Set the Atmos version (without the v prefix)
 ARG ATMOS_VERSION
+ARG OS=linux
+ARG ARCH=amd64
 
-RUN apt-get update && apt-get install -y curl
+RUN apt-get update && apt-get install -y curl git
 
+# Install the Cloud Posse Debian repository
 RUN curl -1sLf 'https://dl.cloudsmith.io/public/cloudposse/packages/cfg/setup/bash.deb.sh' | bash
 
-RUN apt-get update && apt-get install -y terraform helmfile
+# Install OpenTofu
+RUN curl -1sSLf 'https://get.opentofu.org/install-opentofu.sh' | bash -s -- --root-method none --install-method deb
+
+# Install Kustomize binary (required by Helmfile)
+RUN curl -1sSLf "https://raw.githubusercontent.com/kubernetes-sigs/kustomize/master/hack/install_kustomize.sh"  | bash -s -- /usr/local/bin
+
+# Install toolchain used with Atmos
+RUN apt-get -y install terraform kubectl helmfile helm
 
-ADD https://github.com/cloudposse/atmos/releases/download/${ATMOS_VERSION}/atmos_${ATMOS_VERSION}_${OS}_${ARCH} /usr/local/bin/atmos
+# Install the helm-diff plugin required by Helmfile
+RUN helm plugin install https://github.com/databus23/helm-diff
 
-RUN chmod +x /usr/local/bin/atmos
+# Install Atmos
+RUN case ${TARGETPLATFORM} in \
+    "linux/amd64") \
+        OS=linux; ARCH=amd64 ;; \
+    "linux/arm64") \
+        OS=linux; ARCH=arm64 ;; \
+    *) \
+        echo "Unsupported platform: ${TARGETPLATFORM}" && exit 1 ;; \
+    esac && \
+    ATMOS_VERSION=${ATMOS_VERSION#v} && \
+    curl -1sSLf "https://github.com/cloudposse/atmos/releases/download/v${ATMOS_VERSION}/atmos_${ATMOS_VERSION}_${OS}_${ARCH}" -o /usr/local/bin/atmos && \
+    chmod +x /usr/local/bin/atmos