Fix Docker build, use python base image and install Bazel ourselves

Dockerfile

@@ -1,8 +1,15 @@
-FROM gcr.io/cloud-marketplace-containers/google/bazel:3.5.0 AS builder
+FROM python:3.10-bullseye AS builder
+
+RUN apt-get update && apt-get install -y apt-transport-https curl gnupg \
+    && curl -fsSL https://bazel.build/bazel-release.pub.gpg | gpg --dearmor >/usr/share/keyrings/bazel-archive-keyring.gpg \
+    && echo "deb [arch=amd64 signed-by=/usr/share/keyrings/bazel-archive-keyring.gpg] https://storage.googleapis.com/bazel-apt stable jdk1.8" | tee /etc/apt/sources.list.d/bazel.list \
+    && apt-get update && apt-get install -y bazel \
+    && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /wgkex
 
-COPY . ./
+COPY BUILD WORKSPACE requirements.txt ./
+COPY wgkex ./wgkex
 
 RUN ["bazel", "build", "//wgkex/broker:app"]
 RUN ["bazel", "build", "//wgkex/worker:app"]