[building] the vcpkg should be cloned shallowly

[tomFlowee]

When you build ladybird in the official manner, it starts by downloading quite a large external repository called vcpkg.

It occurred to me that you guys probably just clone it without any arguments and the result is that you get the entire historical repo. A git log inside would take you all the way back to 2016.

The suggestion I'd like to make is to clone it with a --depth=1 argument (see git clone --help for details) in order to make the download 90% less (only 6MB).

[rgret-dev]

I think this is problematic since it relies on checking out a specific commit which isn't there when cloning with --depth=1

https://github.com/LadybirdBrowser/ladybird/blob/420949b1349451fdfb004e06625b9efefae24d19/Toolchain/BuildVcpkg.py#L35