Add missing libc6-dev

backend/Dockerfile

@@ -11,7 +11,7 @@ COPY . .
 
 # hadolint ignore=DL3008
 RUN apt-get update \
-  && apt-get install --no-install-recommends -y gcc libffi-dev \
+  && apt-get install --no-install-recommends -y gcc libffi-dev libc6-dev \
   && apt-get clean \
   && rm -rf /var/lib/apt/lists/* \
   && pip install --no-cache-dir -r requirements.txt