Replacing `install` with `install-lib` and `install-bin` is not strictly
necessary just to update the library, but it takes advantage of recent
changes in the new version, and makes the build more minimal.
When no build dir is specified, cmake will warn:
```bash
Preprocessing libmultiprocess...
Configuring libmultiprocess...
CMake Warning:
No source or binary directory provided. Both will be assumed to be the
same as the current working directory, but note that this warning will
become a fatal error in future CMake releases.
```
It's unclear if this will actually ever become an error, but it's also easy
enough to just supply the directory, and save this maybe breaking in
future.
