debian-bootstrap.sh: try using llvm-8 from updates
debian-bootstrap.sh: try using llvm-8 from updates

https://packages.ubuntu.com/bionic-updates/llvm-8

mrkkrp/stackage,stackbuilders/stackage,simonmichael/stackage,soenkehahn/stackage,iand675/stackage,asr/stackage,jonschoning/stackage,wereHamster/stackage,massysett/stackage,fimad/stackage,Daniel-Diaz/stackage,fpco/stackage,athanclark/stackage,clinty/stackage,spencerjanssen/stackage,michalkonecny/stackage