Make the seccomp sandbox work with Ubuntu Xenial and Bionic
Tor's Linux seccomp sandbox fails on Ubuntu Xenial and Bionic, when running tor via chutney.
A --disable-seccomp build succeeds: https://travis-ci.org/teor2345/tor/jobs/622543371?utm_medium=notification&utm_source=github_status
But a build with CHUTNEY_NET_DIR=/tmp fails: https://travis-ci.org/teor2345/tor/jobs/622543706
We should modify tor to work with those glibc versions.