Extend timeouts for clang debug

Looking at e.g.

https://lhcb-nightlies.web.cern.ch/logs/tests/nightly/lhcb-master/1013/x86_64-centos7-clang8-dbg/Brunel/

it appears the clang debug builds take a little longer to run than the gcc builds, so this MR just extends the timeouts a bit to cope.