travis: Add an explicit tmpfs mount
A tempfs mount is missing on fedora 32 which seems to be causing errors
when testcases attempt to write there.
@@ -42,6 +42,7 @@ script:
--volume $HOME/.ccache:/root/.ccache
--volume `pwd`:/build
--volume `pwd`/ci_build_cache/${RUN_ON_CONTAINER}:/root/ci_build_cache/
+ --tmpfs /tmp/
--rm -t $RUN_ON_CONTAINER
bash -c "./opal-ci/build-${RUN_ON_CONTAINER}.sh"
