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
diff --git a/.gitignore b/.gitignore
index 6326775..61d0fcf 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,3 +17,5 @@
 ttcn3/3G+2G_ttcn3.deps
 ttcn3/out/
 ttcn3/make/
+ttcn3/.run.sh
+ttcn3/usr_local