It was added because the default RelWithDebInfo type disabled
assertions, but now that -DNDEBUG is removed from its flags, it is not
necessary to change the build type anymore.
Older automake (travis, *cough*) do not support the
AM_EXTRA_RECURSIVE_TARGETS option, this results in invoking "it-local"
directly in the travis script which relies on an implementation detail.
Since the "it" target is only used by the integration-tests directory,
just avoid the recursive targets. The README.rst suggests to enter the
integration-tests directory anyway.
This is because when we make tar ball, we are no longer under git
control. git submodule does not work there. We instead bundle mruby
source tree in archive. git submodule command is only required when
building from git repository.