There is no functional change here, but they added an error message to
the install output to indicate what host tools need to be installed.
This has tripped some people up, so it seems worth updating to.
And hook it into ladybird.sh for convenience. The script will set up
PATH and other environment variables automatically.
On CI, vcpkg is theoretically already installed on Linux machines, but
not with the right environment variables, and not on macOS. So this also
makes CI use this script to bootstrap vcpkg.
