`gx lock-install`: option to make relative links

[dgrisham]

I recently tried out the feat/gx-lock branch. The symlinks to gx packages created by gx lock-install are absolute paths. However, when Docker is building an image, it will not follow symlinks that lead outside of the build context. To fix this, the symlinks must be relative paths (since the destination paths are still inside of the package/build context).

We could have gx lock-install default to using relative links. However, Windows doesn't support relative paths. This leaves us with two options:

• A --relative option that creates relative paths instead of absolute.
• Detecting the OS and creating relative paths if not on Windows. Relative paths seem like a good default in general. However, this would mean that the default behavior varies based on platform, which may not be ideal.

[Stebalien]

We should just make them relative.

However, Windows doesn't support relative paths.

Windows does support relative symlinks, you're thinking about junctions. Unfortunately, symlinks require https://blogs.windows.com/buildingapps/2016/12/02/symlinks-windows-10/.

However, that's probably fine for gx-go.