(travis) Reshuffle CI workflow, prepare for better instrumentation of failures

No functional changes at this point, the goal was to have no exports in
30_before_script.bash and 40_script.bash, allowing me to run everything
after 20_install.bash in a subshell
(travis) Better diagnostics on *why* a build failed

Especially useful when travis wakes up the OOMKiller

As a bonus add getstatus to all subshells for better idea wtf just went wrong