Implement workaround for Cargo issue on ARMv7

See rust-lang/cargo#8719

docker-src/Dockerfile

@@ -54,17 +54,13 @@ RUN /bin/bash -c 'cd /nginx-1.21.6 && make'
 
 FROM phusion/baseimage:focal-1.1.0 AS builder_py
 
-# Use baseimage-docker's init system.
-CMD ["/sbin/my_init"]
-
-# ...put your own build instructions here...
 RUN apt-get update && /sbin/install_clean curl build-essential libpcre3 libpcre3-dev zlib1g zlib1g-dev libssl-dev openssl libgd-dev libxml2 libxml2-dev uuid-dev git python3 python3-pip python3-dev libffi-dev
-RUN curl https://sh.rustup.rs -sSf | bash -s -- -y
-ENV PATH="/root/.cargo/bin:${PATH}"
 RUN mkdir -p /etc/pyserver
 COPY python-src/* /etc/pyserver/
 RUN python3 -m pip install --upgrade pip
-RUN python3 -m pip install --ignore-installed --upgrade -r /etc/pyserver/requirements.txt
+RUN --mount=type=tmpfs,target=/root/.cargo /bin/bash -c 'curl https://sh.rustup.rs -sSf | bash -s -- -y && \
+	source ~/.cargo/env; \
+	python3 -m pip install --ignore-installed --upgrade -r /etc/pyserver/requirements.txt'
 
 FROM phusion/baseimage:focal-1.1.0
 
@@ -110,4 +106,4 @@ RUN /bin/bash -c "mkdir -p /etc/crontabs/root && echo '*/15 * * * * /usr/bin/pyt
 # RUN /bin/bash -c 'rm -r /etc/nginx/html || : && mkdir -p /etc/nginx/html'
 
 # Clean up APT when done.
-RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*