Make use of the dartaotruntime to reduce container size

By using the dart2aot compiler and using a multi-stage build, we can
reduce the resulting runtime to the dartaotruntime and the pre-built
aot binary - reducing the resulting container size by 1 order of
magnitude. This now resolves #1.

Dockerfile

@@ -1,13 +1,20 @@
-FROM google/dart
+FROM google/dart AS dart-runtime
 
 WORKDIR /app
 
 ADD pubspec.* /app/
 RUN pub get
-ADD . /app
+ADD bin /app/bin/
+ADD lib /app/lib/
 RUN pub get --offline
+RUN dart2aot /app/bin/server.dart  /app/server.aot
+
+FROM bitnami/minideb
+
+COPY --from=dart-runtime /app/server.aot /server.aot
+COPY --from=dart-runtime /usr/lib/dart/bin/dartaotruntime /dartaotruntime
 
 CMD []
-ENTRYPOINT ["/usr/bin/dart", "bin/server.dart"]
+ENTRYPOINT ["/dartaotruntime", "/server.aot"]
 
 EXPOSE 8080