Minor release

This contains all the changes in bsb@4.0.7.
It's 2 versions ahead of bsb for no real reason, it'll stay in sync until bsb reaches 4.0.9 itself (or does a major release).

Fix a bug with requires being generated wrong because -bs-package-ouput in bcc didn't support absolute paths.

Fix a bug with ppx which made them not work when built on postinstall inside node_modules because of missing bs_ppx_tools.exe.