Change `sh` to `bash`, as `sh` is provided by `dash` in Debian, and it lacks
some features (like arrows movement) that makes it easier to use elodie from
the shell
It seems that Alpine's boost-dev package (required to build
pyexiv2) installed Python 3, and this somehow confuses pyexiv2's
build process, which ends up compiling against the Python 3
libraries instead of the Python 2 ones.