[PATCH] D109837: cmake: Deprecate config.guess

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added a comment.

GettingStarted mentions the supported compilers are:

  Clang 3.5
  Apple Clang 6.0
  GCC 5.1
  Visual Studio 2017

Note that the patch doesn't touch the MSVC code path. `-dumpmachine` works for GCC, Clang and Intel C++ Compiler, so really the downloading `config.guess` message will only apply to IBM XL C/C++.
Even for that, looking at `powerpc64-ibm-aix` above, the XL C/C++ code paths are covered.

So perhaps we can just replace `elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang" OR CMAKE_CXX_COMPILER_ID STREQUAL "GNU")` with unconditional `-dumpmachine` call and ask the user to specify `LLVM_HOST_TRIPLE` explicitly if `-dumpmachine` is somehow not available.
User not covered by `-dumpmachine` are expected to be able to come up the triplet by themselves.

If mentioning `config.guess` URL is a problem, just omit it. I don't think there will be a large loss.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D109837/new/

https://reviews.llvm.org/D109837