Add retries to the Docker build

The arm64 ubuntu apt repo `ports.ubuntu.com` is slow, overloaded, and
prone to failing randomly. This adds a retry to the pulls so the build
might succeed eventually. Longer term we should introduce caching and
even maybe a local mirror. For now this hopefully makes the build more
reliable.

Author: MJohnson459

portable.Dockerfile

@@ -8,6 +8,10 @@ ENV DEBIAN_FRONTEND=noninteractive \
 # Prepare directories
 WORKDIR /code
 
+# Make apt resilient to transient ports.ubuntu.com mirror failures
+RUN printf 'Acquire::Retries "6";\nAcquire::http::Timeout "30";\n' \
+      > /etc/apt/apt.conf.d/99-retries
+
 # Copy everything
 COPY . ./
 
@@ -40,6 +44,10 @@ COPY --from=builder /code /code
 
 ENV PATH="/code/venv/bin:$PATH"
 
+# Make apt resilient to transient ports.ubuntu.com mirror failures
+RUN printf 'Acquire::Retries "6";\nAcquire::http::Timeout "30";\n' \
+      > /etc/apt/apt.conf.d/99-retries
+
 # Install shared libraries that we depend on via APT, but *not*
 # the -dev packages to save space!
 # Also run a smoke test on ODM and OpenSfM