Support of new-install for windows

[jneira]

• Currently the default master (new-)install is not supported for windows, like in cabal itself (Symlinking feature not available on Windows)
• As etlas uses lightweight scripts as launchers the support could be create a cmd script file in symlink-bindir that simply executes the launcher script in ${store-dir}\${eta-version}\${package-uid}\bin\${package-name}.cmd
• Not sure if we could do that for all os's or keeping the symlink in unix is better

[rahulmutt]

Not sure if we could do that for all os's or keeping the symlink in unix is better

I suggest that we make the script copying bit a Windows-only thing (just like the launcher scripts). The symlink feature on Unix-based systems is nice.

[jneira]

Investigating a bit i've read that symlinks are supported in windows since vista, with a console tool mklink and the family of CreateSymbolicLink* api calls. Surely i am missing something but i wonder why they are not used in windows by cabal or nix.
It seems until windows 10 you needed admin rights to create them and that wouls be the cause.

[jneira]

There is a pr in cabal about add a install-method flag to allow copy the executables instead symlinking them: haskell/cabal#5870