Making the git-based installation faster

[ffunenga]

While following this:

[1] https://github.com/vlang/v#installing-v---from-source-preferred-method

The git clone command was taking too long, so I tried doing the installation process with:

git clone --depth=1 https://github.com/vlang/v
cd v
make.bat

And it worked faster and fine. I am not immediately seeing a problem with having new users (like myself) just git-clone the fist depth, and it could make the onboarding process smother.

This is just a suggestion. Please close if not useful!