improve erlang.sh installation procedure
fix conversion of build.dir
improve kha_utils:clean_filename/1
fix yaml type mismatch
improve temporary directory path
use runner for dummy container to preserve env changes
fix kha config:get_env/1 output if empty
unify env and lang handling
don't issue unnecessary commands
fix executing multiple jobs in a single build
make use of cd options support in runner
make use of runner in kha_cont_lxc