Adjusted HOME only for pipenv

Nothing later should have been affected, but this is the cleaner way.

Dockerfile

@@ -159,8 +159,8 @@ RUN set -x && \
   groupadd app && \
   useradd -M -d /app -s /bin/false -g app app && \
   # Install non-distro packages
-  cp -at /tmp/ "${HOME}"  && HOME="/tmp/${HOME#/}" && \
-  PIPENV_VERBOSITY=64 pipenv install --system --skip-lock && \
+  cp -at /tmp/ "${HOME}" && \
+  PIPENV_VERBOSITY=64 HOME="/tmp/${HOME#/}" pipenv install --system --skip-lock && \
   # Clean up
   rm /app/Pipfile && \
   pipenv --clear && \