[libcxx-commits] [PATCH] D111356: [runtimes] Use the new "runtimes" build by default and deprecate other builds

[Louis Dionne via Phabricator via libcxx-commits]

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Subscribing folks who might be interested / impacted by this.

Long story short, this commit standardizes on exactly one way of building libc++/libc++abi/libunwind using a system compiler in addition to the existing bootstrapping build that already existed (commonly called the "Runtimes" build). Said differently, it deprecates (but doesn't remove support for) the Standalone build and the LLVM Project build. The Standalone build had been on life support for a while, but the LLVM Project build was the previously documented way of building the runtimes with a system compiler. Fortunately, both should be easy to migrate to the new build - please see the diff for details (in particular the added documentation and the release note).

The current goal is to drop support for the Standalone and the Project builds somewhere in the LLVM 15 time frame.

The benefits of this deprecation/removal is that we'll be able to greatly reduce the complexity of our CMake and provide adequate support for the official ways to build, whereas right now we can't really achieve that due to the large number of ways to build and their complexity. Furthermore, the new way to build using a system compiler will work on embedded platforms and will eventually allow us to remove the requirement to have all the `<root>/llvm` tree available to build the runtimes.

I will also send an email notice to `llvm-dev` and the other lists.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D111356/new/

https://reviews.llvm.org/D111356