I'm sorry that we don't provide a way to access the Linux portion of the file system directly from Windows yet. It's annoying, and we are working to improve it.
For many use cases it suffices to symlink a Windows directory (e.g. /mnt/c/Users/myuser) into your WSL $HOME directory somewhere and do your source work, builds, etc. in that path. This breaks down if you need certain features that aren't supported on these files yet (e.g. chmod), though.
I assure you that we find this annoying too and are working toward a better solution.
For many use cases it suffices to symlink a Windows directory (e.g. /mnt/c/Users/myuser) into your WSL $HOME directory somewhere and do your source work, builds, etc. in that path. This breaks down if you need certain features that aren't supported on these files yet (e.g. chmod), though.
I assure you that we find this annoying too and are working toward a better solution.