ttcn3.sh: build everything inside docker

Replace the previous approach of building outside of docker and mounting
everything inside docker while running tests, with also building
everything inside docker. This prevents incompatibilities between host
system and docker (e.g. different glibc). As nice side-effect,
/usr/local is not filled up anymore.

Change-Id: Ib6db8ffd916c788c9de0b3d51c82e1d7bb3f6828
3 files changed