docker: fix alpine-based image

Dockerfile

@@ -3,13 +3,17 @@ ARG BASE=alpine
 FROM gcr.io/distroless/python3-debian12 AS base-distroless
 FROM python:3.11-alpine AS base-alpine
 
-FROM debian:12-slim AS build
+FROM debian:12-slim AS build-distroless
 RUN apt-get update && \
     apt-get install --no-install-suggests --no-install-recommends --yes python3-venv gcc libpython3-dev && \
     python3 -m venv /venv && \
     /venv/bin/pip install --upgrade pip setuptools wheel
 
-FROM build AS build-venv
+FROM python:3.11-alpine AS build-alpine
+RUN python3 -m venv /venv && \
+    /venv/bin/pip install --upgrade pip setuptools wheel
+
+FROM build-${BASE} AS build-venv
 COPY requirements.txt /requirements.txt
 RUN /venv/bin/pip install --disable-pip-version-check -r /requirements.txt