ci: Add missing errexit to lint CI install

Otherwise, a possible failure is silently ignored.

Also, rename the file, while touching it, to clarify installing is the
first step.

ci/lint_imagefile

@@ -12,7 +12,7 @@ ENV LC_ALL=C.UTF-8
 COPY ./ci/retry/retry /ci_retry
 COPY ./.python-version /.python-version
 COPY ./ci/lint/container-entrypoint.sh /entrypoint.sh
-COPY ./ci/lint/04_install.sh /install.sh
+COPY ./ci/lint/01_install.sh /install.sh
 
 RUN /install.sh && \
   echo 'alias lint="./ci/lint/06_script.sh"' >> ~/.bashrc && \