build: remove the custom build system

[compnerd]

Encouragement for people to move to CMake as the one build system for
Swift!

[gottesmm]

So beautiful...

[compnerd]

@swift-ci please test

[compnerd]

@swift-ci please clean test macOS platform

[compnerd]

CC: @millenomi

[millenomi]

As part of removing this, we must document how to build Core Foundation standalone, since the previous instructions I had relied on the old build system.

Do you have any indications on how to invoke CMake correctly to build CF with CF_DEPLOYMENT_SWIFT off?

[compnerd]

@millenomi - if you have the exact configuration you would like to build, I should be able to tweak the build to get that build working.

[spevans]

I think Docs/GettingStarted.md needs an update as to how to invoke the tests now that ninja test doesn't work since build.ninja is in the build directory.

[spevans]

@swift-ci please test

[spevans]

@compnerd Now that there is a separate PR for updating the docs (#2657) do you want to resurrect this one and finally remove the old build system?

[compnerd]

Yeah, I can do that soonish. Im neck deep in Foundation debugging right now, and don't want to page that out

[shahmishal]

The Swift project moved the default branch to main and deleted master branch, so GitHub automatically closed the PR. Please re-create pull request with main branch.

More detail about the branch update - https://forums.swift.org/t/updating-branch-names/40412