They were 95% the same, so this makes a lot more sense this way. When
group host processes were introduced yabridge only did VST2 bridging,
but we already have a plugin type argument anyways so might as well
reuse that for group hosts.
We had to add an even hackier hack now to get Boost.Process to
interoperate with Asio's IO contexts. This will be replaced later when
we replace Boost.Process.
With the `ghc::filesystem` dependency from the previous commit. If we
can replace the rest of the Boost.Filesystem dependency then we can get
rid the one nasty runtime dependency we have, and it will make
implementing the chainloading simpler since can reuse more code without
bringing in Boost.
We sadly cannot call `shared_library()` and `executable()` in these
subdirectories while still maintaining the same `build/` directory
structure, but this is still much cleaner. All of the other build
artifacts are now also gone from the root of `build/` so it's cleaner
overall.
Robbert van der Helm