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.
We're now getting errors on CI due to gcc-13 being missing. We can
probably be smarter about what packages we install, depending on the
workflow being run. But let's first unblock CI.
The error we get is a bit strange and inconsistent. Some CI runners seem
to already have gcc-13 installed. Others don't and can't find the gcc-13
package without the test Ubuntu toolchain PPA.
Unfortunately a composite action cannot have a `post:` step like
JavaScript actions are allowed to have, so we need to explicitly call
the post/save actions ourselves from the workflow file when we want to
save Toolchain/QEMU/ccache caches.
Co-Authored-By: Timothy Flynn <trflynn89@pm.me>